How often should a dog be treated with tick drops?

Understanding Tick Drops and Their Importance

What are Tick Drops?

Active Ingredients and Their Function

Active ingredients in canine tick‑drop formulations target the nervous system, metabolic pathways, or surface structures of ectoparasites. Their specific actions determine how long protection lasts after each application.

Permethrin – synthetic pyrethroid that disrupts sodium channels, causing rapid paralysis and death of ticks on contact. Provides 2–4 weeks of efficacy.
Fipronil – phenylpyrazole that blocks GABA‑gated chloride channels, leading to uncontrolled neuronal firing. Maintains activity for up to 4 weeks.
Fluralaner – isoxazoline that inhibits GABA‑ and glutamate‑gated chloride channels, preventing nerve transmission. Offers extended protection of 8–12 weeks.
Afoxolaner – isoxazoline with the same channel‑blocking mechanism as fluralaner, delivering 4 weeks of coverage.
Sarolaner – isoxazoline, similar mode of action, effective for 4 weeks.
Selamectin – macrocyclic lactone that interferes with glutamate‑gated chloride channels, affecting parasite neuromuscular function. Protects for 4 weeks.
Imidacloprid – neonicotinoid that binds nicotinic acetylcholine receptors, causing paralysis. Effective for 2–4 weeks.

Each ingredient’s pharmacokinetic profile defines the interval between applications. Compounds with longer half‑lives, such as fluralaner, allow extended dosing schedules, whereas shorter‑acting agents like permethrin require more frequent re‑treatment to sustain tick control.

How They Work on Dogs

Tick‑preventive spot‑ons contain systemic insecticides such as fipronil, imidacloprid, permethrin, or selamectin. After application to the skin between the shoulder blades, the compound spreads through the lipid layer of the skin and enters the bloodstream. When a tick attaches, it ingests the drug while feeding, which disrupts its nervous system or metabolic pathways, leading to rapid paralysis and death.

The absorption phase lasts several hours; during this period the active ingredient reaches concentrations sufficient to affect parasites. Once distributed, the medication remains active in the skin’s oil layer and in the circulation for a defined period, protecting the animal from new infestations.

Typical protection intervals are:

Monthly formulations: one dose every 30 days.
Quarterly formulations: one dose every 90 days.
Extended‑release products: one dose every 120 days.

Choosing the appropriate interval depends on the product’s label, the dog’s weight, and regional tick activity. Consistent application according to the specified schedule maintains therapeutic levels, preventing ticks from completing their feeding cycle and reducing disease transmission risk.

Why Regular Tick Treatment is Crucial

Preventing Tick-Borne Diseases

Applying tick‑preventive medication to a dog is the most reliable method for reducing the incidence of tick‑borne illnesses such as Lyme disease, ehrlichiosis, and anaplasmosis. Consistent administration creates a protective barrier that kills attached ticks before they can transmit pathogens.

Veterinarians generally recommend a monthly schedule for most spot‑on or collar products. The interval aligns with the life cycle of common tick species and the duration of the active ingredients. Deviating from the 30‑day routine shortens protection and increases the chance of infection, especially during peak tick season.

Factors that may require adjustment of the treatment interval include:

Geographic location: Areas with high tick density may benefit from overlapping applications.
Seasonality: In regions where ticks are active year‑round, continuous monthly dosing is advisable; in temperate zones, dosing can be paused during winter months when tick activity drops.
Dog’s lifestyle: Dogs that spend extensive time in wooded or grassy environments, or that travel to endemic areas, may need a supplemental dose between regular applications.
Product type: Some oral preventives maintain efficacy for up to 12 weeks, while most topical solutions require strict 30‑day reapplication.

Monitoring for signs of tick attachment—such as engorged ticks on the coat or unexplained lethargy—provides early detection of potential disease exposure. Prompt removal of any attached ticks, combined with regular preventive treatment, dramatically lowers the risk of pathogen transmission.

Protecting Pet and Human Health

Regular application of tick‑preventive drops safeguards both canine and human health by interrupting the life cycle of ticks that transmit diseases such as Lyme, ehrlichiosis, and anaplasmosis.

Effective control depends on consistent timing. Most products maintain activity for approximately 30 days; therefore, a monthly schedule aligns with the pharmacokinetics of the active ingredients and provides continuous protection.

Factors that may require adjustment include:

Geographic risk: Areas with high tick prevalence may demand uninterrupted monthly treatment throughout the year.
Seasonal exposure: In regions where ticks are active only from spring to early fall, treatment can be limited to that period, but missing a dose can create a gap in protection.
Dog’s lifestyle: Dogs that frequent wooded trails, parks, or farms encounter greater tick pressure and should receive drops without interruption.

Human health benefits stem from reduced environmental tick density and lower chance of accidental bites. When a dog carries fewer ticks, the probability of a tick attaching to a person declines markedly.

Veterinary guidelines typically advise:

Initiate treatment at the start of the tick season.
Apply drops every 4 weeks without interruption.
Continue through the end of the season, even if the dog appears tick‑free, to eliminate any residual larvae or nymphs.

Adhering to this regimen minimizes the risk of tick‑borne illnesses in pets and their owners, preserving overall household health.

Factors Influencing Treatment Frequency

Product-Specific Guidelines

Manufacturer Recommendations

Manufacturers base their dosing schedules on the pharmacokinetics of the active ingredient and the intended protection period. Most spot‑on products are formulated to provide continuous efficacy for a specific number of days, and the label specifies the interval at which the medication should be reapplied.

Products containing imidacloprid or fluralaner typically guarantee protection for 30 days; re‑application is required monthly.
Formulations with afoxolaner or sarolaner often extend coverage to 28 days; owners should treat the dog once every four weeks.
Certain long‑acting preparations, such as those using isoxazolines with higher dose concentrations, claim protection for up to 90 days; the label directs a three‑month re‑treatment cycle.
Seasonal products marketed for high‑risk periods may advise weekly or bi‑weekly applications, especially in regions with rapid tick activity peaks.

Labels also adjust the interval according to the dog’s weight class. For example, a 10‑kg dog may receive a single dose per month, while a dog over 20 kg may need a larger volume but the same monthly schedule. Some manufacturers include a “continuous protection” clause that permits uninterrupted coverage as long as the next dose is administered before the previous one expires.

Compliance with the exact timing on the package ensures the active ingredient remains at therapeutic levels in the skin and hair follicles, preventing tick attachment and disease transmission. Deviating from the recommended interval—either by delaying or by applying too frequently—can reduce efficacy and increase the risk of resistance development.

Duration of Efficacy

Effective tick control drops remain active for a defined period after application, establishing the interval between treatments. Most commercially available spot‑on formulations provide protection for 30 days; this is the standard schedule recommended by manufacturers and veterinary guidelines. Some products extend efficacy to 45 days, while a minority claim up to 60 days of protection. Shorter‑acting drops, typically based on older active ingredients, maintain activity for 14 days and require bi‑weekly reapplication.

Key factors influencing the duration include:

Active ingredient – Acaricides such as fipronil, fluralaner, and sarolaner differ in residual activity, with newer compounds generally offering longer coverage.
Dog’s weight and coat type – Heavier or double‑coated dogs may experience slower absorption, potentially reducing the effective period by a few days.
Environmental exposure – Frequent swimming or heavy rain can wash away the product, shortening protection.

When planning a treatment schedule, align the re‑application interval with the longest proven efficacy of the chosen product, adjusting for the dog’s specific characteristics and local tick pressure. Consistent adherence to this interval ensures continuous protection and reduces the risk of infestation.

Environmental Tick Activity

Seasonal Variations

Tick‑preventive treatments should align with the local activity pattern of ixodid ticks, which fluctuates throughout the year. In regions where temperatures rise above 10 °C (50 °F) for extended periods, tick populations increase sharply in spring and remain high through summer and early autumn. During these months, monthly applications of tick‑dropping products are recommended to maintain consistent protection. When temperatures consistently fall below the threshold for tick development, typically in late autumn and winter, the risk diminishes; a reduced schedule—often every two months or suspension until the next active season—is sufficient.

Spring (March–May): Begin monthly dosing as soon as outdoor activity resumes and temperatures exceed 10 °C.
Summer (June–August): Continue monthly dosing; consider a short‑term boost if heavy vegetation or high humidity intensifies tick presence.
Early Autumn (September–October): Maintain monthly dosing; assess local tick reports to decide on continuation.
Late Autumn/Winter (November–February): Shift to bi‑monthly dosing or pause treatment if temperatures remain below 10 °C for more than four weeks.

Adjustments may be necessary for microclimates, altitude, or unusually warm winters. Monitoring local veterinary advisories and tick‑activity alerts provides the most reliable guidance for modifying the treatment schedule.

Geographic Location

Geographic location determines the timing and frequency of acaricide applications for dogs because tick activity varies with climate, altitude and local species distribution. In temperate zones with cold winters, adult ticks become inactive after the first frost, allowing a single monthly application from early spring until the first frost of autumn. In subtropical and tropical regions where temperatures remain above 10 °C year‑round, ticks can be active continuously; therefore, monthly treatments should be maintained throughout the entire year.

Key regional patterns:

Northern United States, Canada, northern Europe – apply drops once a month from March to October; suspend treatment during November‑February when tick activity is negligible.
Mid‑latitude areas (e.g., central United States, southern Europe) – apply drops monthly from February to November; consider an additional dose in early spring if a warm spell precedes typical tick emergence.
Southern United States, Mediterranean coast, parts of Australia – apply drops every month year‑round; increase to bi‑weekly during peak summer months (June‑August) when tick populations surge.
High‑altitude or mountainous regions – limit applications to the brief warm period, usually May‑July, because ticks are active only for a few weeks.

Local veterinary guidelines and tick‑borne disease prevalence should also influence the schedule. Areas with documented cases of Lyme disease, ehrlichiosis or babesiosis often recommend continuous protection, even when overall tick activity appears low. Adjustments based on seasonal weather forecasts—such as an early warm spring—can prevent gaps in coverage.

Dog's Lifestyle and Exposure Risk

Outdoor Activities

Dogs that spend time outside are exposed to ticks more frequently than indoor pets, so the timing of topical acaricide application must reflect the level of outdoor exposure.

For dogs that are taken on walks in tick‑prone areas a few times a week, a monthly application is sufficient, provided the product’s label specifies a 30‑day protection period.

When a dog participates in regular hiking, camping, or hunting trips—activities that increase contact with vegetation and wildlife—apply the drops at the start of each trip and repeat the treatment every 2 weeks if the label allows a shorter interval, or otherwise maintain the standard monthly schedule but do not miss a dose.

If a dog’s outdoor routine includes daily runs in wooded parks or frequent visits to fields with known tick infestations, consider a bi‑weekly regimen, using a product approved for such frequency, to maintain continuous coverage.

In low‑risk situations, such as occasional weekend outings in tick‑free zones, the standard monthly schedule remains appropriate; additional applications are unnecessary.

Key points for practitioners and owners:

Assess the dog’s typical outdoor environment (urban park, rural trail, high‑grass field).
Match the product’s labeled protection duration to the exposure level.
Do not exceed the maximum recommended frequency; over‑application can cause toxicity.
Re‑apply after swimming, heavy rain, or washing, as these can diminish efficacy.

Consistent adherence to a schedule aligned with the dog’s outdoor activity pattern ensures effective tick control and reduces the risk of tick‑borne diseases.

Contact with Other Animals

Dogs that regularly interact with other animals face a higher risk of acquiring ticks. Direct contact with pets, livestock, or wildlife introduces parasites that may not be present in the home environment. Consequently, the interval between applications of tick‑preventive drops should reflect the level and type of exposure.

Higher exposure situations typically require more frequent treatment:

Daily visits to dog parks, boarding facilities, or grooming salons – apply drops every 2 weeks.
Weekly walks in wooded or grassy areas where wildlife is common – apply drops every 3 weeks.
Occasional contact with other pets during playdates or short outings – maintain the standard monthly schedule.
Minimal outdoor activity and no contact with other animals – a single monthly application is sufficient.

Adjust the regimen if the dog shows signs of tick attachment or if a known tick‑infested animal has been present. Regular inspection of the coat, especially after social interactions, helps identify gaps in protection. When increased risk is confirmed, shorten the interval by one week and resume the appropriate schedule once exposure decreases. This responsive approach ensures continuous protection while avoiding unnecessary medication.

Individual Dog Health Considerations

Age and Breed

Age influences the timing of acaricide applications. Puppies under eight weeks are typically exempt from topical treatments because their skin is still developing and systemic absorption may be higher. Once the puppy reaches eight weeks, a reduced dose—often half the adult amount—can be applied every four weeks, matching the label’s minimum interval. Adult dogs, defined as twelve months and older, generally receive the full dose at the standard interval of four weeks. Senior dogs (seven years and older) may require a longer interval if they have reduced metabolism or skin conditions; extending to six‑week intervals can maintain efficacy while minimizing potential irritation.

Breed characteristics also affect the schedule. Breeds with dense, double coats (e.g., Siberian Huskies, Alaskan Malamutes) retain the product longer, allowing the standard four‑week interval. Short‑haired or hairless breeds (e.g., Greyhounds, Chinese Crested) lose the formulation more quickly, which may necessitate a three‑week interval during peak tick season. Breeds prone to skin sensitivities (e.g., Bulldogs, Shar-Peis) should be monitored for adverse reactions; a conservative three‑week interval with a reduced dose can prevent buildup while still providing protection.

Practical recommendations:

Puppies 8–12 weeks: half dose, every 4 weeks.
Adult dogs: full dose, every 4 weeks.
Seniors: full dose, every 4–6 weeks, based on health status.
Double‑coated breeds: standard 4‑week interval.
Short‑haired or hairless breeds: consider 3‑week interval in high‑risk periods.
Sensitive‑skin breeds: monitor closely; adjust dose or interval as needed.

Pre-existing Conditions

Pre‑existing medical conditions can alter the safe interval for applying acaricide spot‑on products. Dogs with liver or kidney disease may process the active ingredients more slowly, requiring a longer gap between applications to prevent accumulation. Animals receiving chronic corticosteroid therapy have suppressed immune responses, which can increase susceptibility to tick‑borne infections; a more frequent schedule may be warranted, but only under veterinary supervision to avoid adverse drug interactions.

When a canine has a history of allergic reactions to any component of the tick‑preventive formulation, the veterinarian should confirm tolerance before establishing a routine. In such cases, the professional might recommend a reduced dosage or an alternative class of product, which could change the timing of re‑application.

Key considerations for adjusting the treatment schedule:

Hepatic or renal impairment → extend interval, monitor blood work.
Immunosuppressive medication → evaluate risk, possibly increase frequency with vet approval.
Documented hypersensitivity → confirm safe product, modify dosing schedule accordingly.

Best Practices for Applying Tick Drops

Proper Application Technique

Safely Administering the Product

When applying spot‑on tick medication, follow a strict protocol to avoid accidental exposure and ensure efficacy. First, confirm the product’s concentration matches the dog’s weight; most manufacturers list dosage ranges in milligrams per kilogram. Measure the exact amount required and do not exceed the recommended dose.

Prepare the application site by parting the hair at the base of the neck, directly on the skin. Apply the entire dose in a single spot, allowing the liquid to seep into the skin without spreading it over a larger area. Avoid contact with the dog’s eyes, nose, or mouth during and after application.

After treatment, keep the dog restrained for at least one minute to prevent licking or grooming of the spot. Wash hands thoroughly with soap and water; use gloves if available. Dispose of any unused product in accordance with local hazardous‑waste guidelines.

Store the medication in a cool, dry place away from direct sunlight and out of reach of children and other animals. Check expiration dates before each use; expired formulations lose potency and may cause skin irritation.

Key safety checkpoints:

Verify weight‑specific dosage.
Apply directly to skin at the nape.
Prevent licking for a minimum of 60 seconds.
Wash hands and clean equipment after each use.
Keep product sealed, cool, and within its shelf life.

Areas to Target and Avoid

Tick‑spot‑on products are typically applied every 30 days, although some formulations extend protection to 8 weeks; adhering to the label interval prevents gaps in coverage.

Effective application requires placing the drop on skin that the dog cannot lick. Target sites include:

The dorsal midline, midway between the shoulder blades.
The neck region, just behind the ears.
The base of the tail, on the skin rather than the fur.
The inner thigh or flank, where the fur is thin and the skin is accessible.

Avoid locations where the medication can be ingested or where it may cause irritation:

Areas with dense fur, such as the top of the head or muzzle.
The paws, pads, or between toes.
Open wounds, irritated skin, or allergic lesions.
The anal region and genital openings.

Applying the product precisely to the recommended zones and steering clear of prohibited spots maximizes efficacy and minimizes the risk of adverse reactions.

Potential Side Effects and What to Do

Mild Reactions

Tick‑preventive spot‑on treatments are typically applied monthly, though some formulations allow a six‑week interval. When used according to label directions, most dogs experience only minor, transient reactions.

Common mild reactions include:

Slight redness or irritation at the application site
Temporary hair loss around the spot
Minor itching or scratching for a few hours
Low‑grade fever lasting less than 24 hours

These effects usually resolve without veterinary intervention. If a reaction persists beyond 48 hours or worsens, discontinue the product and consult a professional.

Adjusting the application schedule may reduce the likelihood of mild responses. For dogs with a history of skin sensitivity, extending the interval to six weeks or switching to a different active ingredient can be effective. Always follow the manufacturer’s guidelines and monitor the animal after each dose.

Severe Adverse Events

Severe adverse events can occur after topical tick‑preventive applications, and their potential seriousness directly influences how often the product should be used. Systemic toxicity, anaphylaxis, and necrotic skin lesions are documented reactions that may develop after a single dose or after repeated exposure, especially when dosing intervals are shortened beyond the label recommendation.

Typical manifestations of a severe reaction include:

Rapid onset of facial swelling, hives, or difficulty breathing;
Sudden collapse, seizures, or loss of consciousness;
Extensive ulceration, necrosis, or deep dermal erosion at the application site;
Persistent vomiting, diarrhea, or marked lethargy.

Risk factors comprise pre‑existing allergies, compromised liver or kidney function, concurrent administration of other ectoparasitic products, and improper dosing (e.g., using a concentration intended for larger breeds on a small dog). Veterinary assessment is required at the first sign of any listed symptom; immediate discontinuation of the product and emergency treatment may be necessary.

When planning the treatment schedule, veterinarians should:

Verify the dog’s weight and health status before each application;
Adhere strictly to the manufacturer‑specified interval, typically four weeks, unless a shorter interval is justified by a high‑risk environment and the dog has demonstrated tolerance;
Conduct a brief observation period after each dose to detect early signs of severe toxicity;
Adjust the interval or switch to an alternative control method if any adverse event is recorded.

Failure to recognize severe reactions can lead to irreversible damage or fatal outcomes, underscoring the need for cautious frequency management and prompt veterinary intervention.

Combining with Other Tick Prevention Methods

Collars and Sprays

Collars and sprays provide continuous protection against ticks, reducing the need for frequent topical applications.

Collars are impregnated with acaricides that release active ingredients over time. Most products maintain efficacy for 8–12 weeks, after which the collar should be replaced. Effectiveness depends on proper fit—tight enough to stay in place but loose enough for two fingers to slide underneath.

Sprays deliver a rapid dose of insecticide directly onto the coat. They typically protect for 2–4 weeks, depending on the formulation and environmental exposure. Application should cover the entire body, avoiding the eyes and mucous membranes. Re‑application is required when the protective period expires or after heavy bathing, swimming, or intense physical activity.

Typical re‑treatment intervals

Collar replacement: every 8–12 weeks
Spray re‑application: every 2–4 weeks, or sooner after water exposure

When using collars or sprays alongside tick drops, align the schedules so that no gap in protection occurs. For example, replace a collar at the end of its 10‑week lifespan and apply a spray 2 weeks later if the drop regimen has been paused. This coordinated approach maintains consistent tick control while minimizing the number of topical treatments required.

Environmental Control

Effective tick management for dogs depends as much on the surrounding environment as on the timing of topical treatments. Reducing tick habitats lowers the number of infestations and can extend the interval between applications without compromising protection.

Key environmental strategies include:

Maintaining short grass and trimming hedges to eliminate preferred questing sites.
Removing leaf litter, tall weeds, and brush where ticks hide.
Keeping compost piles and woodpiles dry and covered.
Treating outdoor resting areas with approved acaricides or diatomaceous earth.
Restricting dog access to high‑risk zones such as dense woodland or tall grasses during peak tick activity seasons.

Seasonal considerations affect the required frequency of drops. In regions with a short tick season, a single monthly application may suffice if environmental controls are rigorously applied. In areas with prolonged activity, continuous monthly treatments remain advisable, even when habitats are managed, to address residual tick pressure.

Combining regular topical prophylaxis with systematic habitat modification creates a layered defense, minimizes the risk of disease transmission, and optimizes the cost‑effectiveness of tick control programs.

Consulting with Your Veterinarian

Tailored Treatment Plans

Assessing Individual Needs

Assessing a dog’s individual needs is essential for determining the optimal frequency of tick‑drop administration. Veterinary guidelines provide a baseline schedule, but adjustments depend on specific variables.

Key factors to evaluate:

Geographic risk – Areas with high tick prevalence may require more frequent applications.
Seasonal activity – Tick activity peaks in spring and summer; intervals often shorten during these periods.
Lifestyle – Dogs that spend extensive time outdoors, hunt, or travel to rural zones face greater exposure.
Health status – Puppies, older dogs, or animals with compromised immunity may need stricter protection.
Product characteristics – Some formulations maintain efficacy for up to eight weeks, while others last four weeks; follow the label specifications.

The assessment process should include a review of the dog’s recent environment, any recent travel, and current health conditions. Owners should document exposure patterns and discuss them with a veterinarian, who can tailor the treatment interval accordingly. Regular reevaluation—at least quarterly—ensures the schedule remains aligned with changing risk factors and the dog’s condition.

Addressing Concerns

Dog owners frequently question how often tick‑preventive drops should be applied. Concerns center on safety, effectiveness, resistance, and cost, all of which influence adherence to a treatment plan.

Safety: Most products are approved for monthly use; applying more often does not increase protection and may raise the risk of skin irritation.
Effectiveness: Efficacy diminishes after the labeled period; re‑application before the end of that interval offers no additional benefit.
Resistance: Overuse does not prevent resistance and can accelerate it; following the recommended interval preserves product potency.
Cost: Unnecessary extra doses increase expense without improving protection.

Veterinarians generally advise a schedule aligned with the product’s label, typically every 30 days. Adjustments may be needed for:

High‑risk environments (e.g., dense woods, endemic areas) – maintain the standard interval; supplement with environmental control rather than more frequent drops.
Low‑risk indoor dogs – the same interval remains appropriate; skipping doses can leave the animal vulnerable during seasonal peaks.

Consistent monthly application, combined with regular tick checks, provides reliable protection while minimizing adverse effects and unnecessary expenditure.

When to Adjust the Treatment Schedule

Changes in Environment

Environmental conditions directly influence the timing of tick‑preventive applications for dogs. Warmer temperatures accelerate tick life cycles, increasing the risk of infestation during spring and summer months. In regions where seasonal temperatures rise earlier or remain elevated longer, the interval between treatments should be shortened, often to every three weeks rather than the standard four‑week schedule.

Seasonal humidity also affects tick activity. High moisture levels sustain tick populations, extending the period during which dogs are vulnerable. When humidity spikes—such as during rainy seasons—owners should consider adding an extra dose of tick drops or switching to a more frequent regimen.

Key environmental factors that modify preventive frequency include:

Average monthly temperature trends
Relative humidity levels
Presence of dense vegetation or leaf litter in the dog's environment
Seasonal migration patterns of local wildlife hosts

Monitoring these variables enables precise adjustment of tick‑preventive intervals, ensuring continuous protection while avoiding unnecessary applications.

Health Status Updates

Regular health status updates provide the data needed to set an appropriate interval for canine tick‑preventive spot‑on products.

A baseline schedule of one application every 30 days maintains effective protection for most healthy dogs. This interval aligns with the product’s claimed residual activity and the life cycle of common tick species.

Adjustments based on recent health information may be necessary:

Weight fluctuations – rapid loss or gain can alter the surface area covered; re‑evaluate dosage after a 10 % change.
Dermatological conditions – active skin lesions or allergies may require a temporary pause or a switch to a hypoallergenic formulation.
Concurrent medications – drugs that affect liver enzymes can modify the metabolism of the active ingredient; consult a veterinarian before continuing the routine.
Seasonal exposure – increased outdoor activity during peak tick season (spring‑early autumn) may justify a supplemental application after 21 days; reduce to the standard 30‑day interval when risk declines.

Document each health assessment, noting date, weight, skin status, and any medication changes. Compare the record with the upcoming application date; if a discrepancy appears, adjust the schedule promptly to preserve continuous protection.

Consistent monitoring and timely record‑keeping ensure that the preventive regimen remains aligned with the dog’s current health profile, minimizing gaps in tick control.