At what temperature do lice and nits die in washing?

Understanding Lice and Nits

The Lifecycle of Head Lice

Adult Lice Survival

Adult head lice are highly vulnerable to heat. Laboratory studies show that exposure to water at 54 °C (130 °F) for a minimum of five minutes results in complete mortality. Temperatures of 49 °C (120 °F) kill most insects within ten minutes, but a small fraction may survive longer exposures. Reliable eradication is achieved at 60 °C (140 °F) even with brief contact; a one‑minute soak is sufficient to eliminate all adults.

49 °C (120 °F) – ten‑minute exposure kills the majority of adults.
54 °C (130 °F) – five‑minute exposure guarantees death.
60 °C (140 °F) – one‑minute exposure ensures complete elimination.

Water below 30 °C (86 °F) does not affect adult lice viability; they remain active after prolonged washing at typical cold‑water settings. Adding detergent does not increase thermal lethality, though it assists in removing insects from fabric. For effective laundering, set the machine to a cycle that reaches at least 54 °C and maintains that temperature for the duration specified above.

Nit Development and Hatching

Nit development proceeds through a defined timeline. Adult female lice deposit eggs (nits) on hair shafts, attaching them with a cement-like substance. The incubation period lasts 7–10 days at typical indoor temperatures (20‑25 °C). During this phase the embryo undergoes cellular division, forming a visible oval shell. Hatching occurs when the nymph breaks through the shell, usually after the embryo reaches full size and the shell softens.

Temperature directly influences both development speed and survival. Below 15 °C, embryonic growth slows markedly, extending incubation to 14 days or more. Above 30 °C, rapid development may reduce the incubation period to 5 days, but extreme heat also compromises viability.

Thermal thresholds for lethal treatment in laundering are well documented:

50 °C (122 °F) for at least 10 minutes destroys most active lice and prevents hatching of viable nits.
60 °C (140 °F) for 5 minutes guarantees mortality of both adult insects and fully formed eggs.
Temperatures below 45 °C (113 °F) do not reliably kill nits; some eggs may survive and hatch after washing.

Effective laundering therefore requires water temperature of at least 50 °C combined with sufficient exposure time to ensure complete eradication of the egg stage.

Vulnerabilities to Temperature

Lice (Pediculus humanus capitis) and their eggs (nits) are highly susceptible to heat. Exposure to temperatures above the organism’s thermal tolerance disrupts protein structures and leads to rapid mortality.

Adult lice: 50 °C (122 °F) for 5 minutes or 55 °C (131 °F) for 1 minute eliminates virtually all specimens.
Nits: 55 °C (131 °F) sustained for at least 10 minutes is required to break the protective shell and kill the developing embryo; lower temperatures (≈45 °C/113 °F) may reduce viability but do not guarantee complete eradication.

Washing cycles that reach or exceed 60 °C (140 °F) for a typical 30‑minute duration provide a safety margin for both stages. Detergent alone does not compensate for insufficient heat; the thermal component is the decisive factor.

Temperatures below 40 °C (104 °F) allow survival of both adults and nits, even with prolonged exposure. Cold water washes, unless combined with chemical treatments, fail to achieve disinfestation.

Consequently, laundering infested fabrics at 60 °C (140 °F) or higher, maintaining the temperature for the full wash cycle, ensures reliable elimination of lice and their eggs.

Temperature Thresholds for Lice and Nits in Washing

Efficacy of Hot Water Washing

Minimum Temperature for Lice Mortality

Lice and their eggs (nits) are sensitive to heat, but the temperature required to ensure complete mortality is higher than typical laundry settings. Research indicates that exposure to water at 54 °C (130 °F) for at least five minutes kills both adult insects and nits. Temperatures below this threshold may eliminate some adults but often leave viable eggs, leading to reinfestation after washing.

Key temperature‑time thresholds:

54 °C (130 °F) – minimum for full kill, 5 min exposure.
60 °C (140 °F) – reliable kill, 10 min exposure.
71 °C (160 °F) – rapid kill, 2 min exposure.

Practical guidance for laundering infested items:

Set the washing machine to the hottest cycle available, aiming for at least 54 °C.
Extend the wash duration to meet the minimum exposure time.
Use a high‑heat dryer cycle (≥70 °C) for an additional 20 minutes, which further guarantees eradication.

If the machine cannot reach the required temperature, alternative methods such as boiling water immersion for ten minutes or professional steam cleaning are effective substitutes. Consistently applying these temperature standards prevents surviving nits and reduces the risk of recurrence.

Minimum Temperature for Nit Mortality

The minimum temperature that reliably kills lice eggs in a washing cycle is higher than the temperature needed to eliminate adult insects. Laboratory tests show that exposure to water at 54 °C (130 °F) for at least 10 minutes destroys adult lice, but viable nits persist unless the temperature is increased.

- 60 °C (140 °F) for 5 minutes – kills >99 % of nits, confirmed by entomological studies.
- 55 °C (131 °F) for 30 minutes – achieves comparable mortality when combined with vigorous agitation.
- Below 50 °C (122 °F) – insufficient; nits remain viable even after extended cycles.

Effective laundering therefore requires either a wash setting that reaches 60 °C or a lower temperature paired with an extended dwell time and high mechanical action. Adding a high‑heat dryer cycle (≥70 °C) further ensures complete eradication.

Factors Affecting Temperature Effectiveness

Wash Cycle Duration

The effectiveness of a wash cycle against head‑lice and their eggs depends on both water temperature and exposure time. Lice and nits are unable to survive sustained contact with water at or above 55 °C (131 °F). At this temperature, a minimum of five minutes of continuous agitation is sufficient to ensure mortality. Lower temperatures require longer exposure; for example, water at 45 °C (113 °F) must remain in motion for at least fifteen minutes, while 40 °C (104 °F) demands thirty minutes or more, and temperatures below 40 °C do not reliably kill the insects.

Recommended wash cycle parameters

55 °C (131 °F) – 5 min minimum agitation
50 °C (122 °F) – 8 min minimum agitation
45 °C (113 °F) – 15 min minimum agitation
40 °C (104 °F) – 30 min minimum agitation

Select a cycle that maintains the specified temperature throughout the stated duration. Heavy‑duty or sanitizing cycles on most modern machines meet these criteria, provided the load is not oversized and the machine’s thermostat is accurate. After washing, immediate drying at high heat (≥60 °C) further reduces any surviving organisms.

Water Penetration and Fabric Type

Water penetration determines how effectively heat reaches parasites embedded in clothing. Fabrics that absorb water quickly allow the wash temperature to act uniformly on all fibers, ensuring that lice and their eggs are exposed to lethal heat. Dense or hydrophobic materials impede moisture flow, creating cooler pockets where nits may survive even when the wash water reaches the recommended temperature.

Fabric characteristics influence temperature retention during the cycle. Cotton and rayon, being highly absorbent, reach the set water temperature within seconds and maintain it throughout the wash. Polyester, nylon, and acrylic repel water, slowing heat transfer and often requiring a longer dwell time at the target temperature to guarantee mortality. Wool, with its natural oils, also slows penetration and may protect nits unless the wash includes an extended hot‑water soak.

Highly absorbent (cotton, linen, rayon): rapid heat distribution, effective at 130 °F (54 °C) or higher for 10 minutes.
Moderately absorbent (polyester blends, viscose): slower heat spread, recommend 140 °F (60 °C) with a minimum 15‑minute soak.
Low absorbent (synthetic fleece, acrylic): poor water uptake, advisable to pre‑soak or increase temperature to 150 °F (65 °C) for at least 20 minutes.

Selecting the appropriate wash temperature must account for the fabric’s ability to let water—and thus heat—penetrate fully. Adjusting temperature or extending exposure compensates for fabrics that limit moisture flow, ensuring complete eradication of lice and nits.

Practical Washing Guidelines for Infested Items

Preparing Items for Washing

Sorting and Segregation

Washing at temperatures of 130 °F (54 °C) or higher reliably kills both adult lice and their eggs. Temperatures below this threshold may only incapacitate adult insects, leaving viable nits that can re‑infest.

Effective elimination depends on proper sorting of laundry before the wash. Separate garments that can withstand high heat from those that cannot; mix of heat‑tolerant items (cotton, polyester blends) with heat‑sensitive fabrics (wool, silk) reduces overall water temperature and compromises efficacy. Grouping only heat‑tolerant items ensures the machine reaches the required temperature throughout the load.

Segregation extends to accessories and personal items. Place hats, scarves, pillowcases, and bedding containing lice in a dedicated hot‑wash batch. Keep non‑contaminated clothing in a separate load to avoid cross‑contamination and to allow the use of lower temperatures for those items.

Practical sorting and segregation steps

Identify all items that have been in contact with an infested person.
Classify each item by fabric durability at ≥130 °F.
Create two piles: heat‑tolerant (wash together at ≥130 °F) and heat‑sensitive (wash separately using alternative treatments).
Include all headwear, bedding, and towels in the heat‑tolerant pile.
After washing, dry at the highest setting compatible with the fabric; dryer heat above 130 °F provides additional lethality.

By rigorously sorting and segregating laundry, the washing process consistently achieves the temperature needed to eradicate lice and nits, preventing recurrence.

Pre-Soaking Recommendations

Pre‑soaking garments, bedding, and accessories before machine laundering enhances the likelihood that lice and their eggs will be exterminated. The soak creates a uniform thermal environment and allows chemical agents to penetrate the protective shells of nits.

Use water at or above 130 °F (54 °C). This temperature exceeds the thermal threshold that kills both adult lice and nits within minutes.
Add a detergent formulated for hot‑water cycles. Enzymatic cleaners break down the protein matrix of nit cement, exposing the egg to heat.
Include a 10‑minute soak period before the wash cycle. Extended exposure ensures heat reaches all layers of fabric and tight seams.
For extra efficacy, introduce 1 cup of white vinegar or ½ cup of lemon juice per gallon of water. The acidity weakens the nit’s outer coating, facilitating heat penetration.
Agitate gently during soaking. Mild mechanical movement dislodges nits from hair shafts and fabric fibers, preventing shelters that could shield them from temperature.

After the pre‑soak, run a full hot‑water wash followed by a high‑heat dryer cycle (minimum 130 °F) to complete the eradication process.

Washing Machine Settings

Temperature Selection

Washing garments and bedding at sufficiently high temperatures is a reliable method for eliminating head lice and their eggs. Scientific tests show that live insects cannot survive exposure to water at 54 °C (130 °F) for more than a few seconds, while the protective shells of the eggs require a slightly higher heat level to rupture.

54 °C (130 °F) – lethal to adult lice and nymphs.
60 °C (140 °F) – reliably destroys nits.
Minimum exposure time – 5 minutes at the target temperature ensures complete mortality.

When selecting a wash cycle, set the thermostat to exceed 54 °C and verify that the machine maintains that temperature for the full duration of the main rinse. If the fabric label permits, use the hottest setting available; otherwise, pre‑soak items in hot water before laundering at the highest safe temperature.

For delicate textiles that cannot withstand high heat, alternative decontamination includes sealing items in a plastic bag and exposing them to a dryer on the hottest setting (≥60 °C) for at least 20 minutes, or using a steam treatment that reaches comparable temperatures.

Choosing the appropriate temperature eliminates the need for chemical treatments and reduces the risk of reinfestation. Consistent use of the described heat parameters guarantees eradication of both insects and their resistant eggs.

Cycle Type and Duration

The effectiveness of laundering against head‑lice and their eggs depends on both the water temperature achieved and the length of the wash cycle. Research shows that exposure to water at 55 °C (131 °F) for a minimum of five minutes destroys adult insects, while eggs require slightly higher heat or longer exposure. A cycle that reaches at least 60 °C (140 °F) and maintains that temperature for ten minutes guarantees complete eradication of both stages.

Typical machine settings that meet these criteria are:

Hot‑wash cycle: water temperature 60 °C or higher, duration 30–45 minutes. The extended run time ensures the thermal threshold is maintained throughout the load.
Sanitize or steam cycle: temperature 65 °C or higher, duration 15–20 minutes. Steam adds moisture that penetrates fabric, enhancing lethality against nits.
High‑temperature rinse: water temperature 55 °C, followed by a final rinse at 60 °C, total time 20 minutes. Sufficient for adult lice but less reliable for eggs unless combined with a longer soak.

If the machine offers a “thermal disinfection” option, it typically cycles to 70 °C for five minutes, then cools; this protocol is the most efficient for eliminating all life stages in a single wash. For items that cannot withstand high heat, extended soaking in water heated to 55 °C for at least 30 minutes, followed by a hot‑dry cycle, provides an alternative method.

Drying and Post-Washing Treatment

High Heat Drying Benefits

High‑temperature drying is a reliable method for eradicating head‑lice infestations after laundering. When garments, bedding, or towels are exposed to dryer heat of 130 °F (54 °C) or higher for at least 10 minutes, both adult lice and their eggs lose viability. The combination of sustained heat and tumbling action disrupts the protective coating of nits, preventing re‑infestation.

Key temperature guidelines for effective drying:

130 °F (54 °C) minimum – sufficient to kill most adult lice within 10 minutes.
140 °F (60 °C) preferred – ensures rapid mortality of nits, reducing the required exposure time to 5 minutes.
150 °F (66 °C) optimal – guarantees complete destruction of resistant eggs, even in dense fabrics.

Applying these heat settings after a wash cycle that already reaches at least 120 °F (49 °C) maximizes the lethal effect. The dryer’s airflow also helps remove detached insects, providing an additional mechanical barrier to survival. Consistent use of high‑heat drying eliminates the need for chemical treatments and reduces the risk of reinfestation.

Items Not Suitable for Washing

Lice and their eggs (nits) are eliminated when laundry reaches temperatures that denature their proteins, typically around 130 °F (54 °C) for a minimum of 10 minutes. Not all household items can endure such heat, and many cannot be safely processed in a washing machine without compromising their integrity or effectiveness against infestation.

Delicate fabrics (silk, lace, chiffon): low‑temperature washes cause shrinkage, distortion, or loss of finish; high heat may melt fibers.
Wool and cashmere garments: prone to felting and shrinkage at temperatures above 95 °F (35 °C); agitation can cause pilling.
Synthetic performance wear (spandex, moisture‑wicking polyester): heat can degrade elasticity and moisture‑management properties; some coatings melt at 120 °F (49 °C).
Leather, suede, and faux‑leather items: water absorption leads to warping, staining, or loss of suppleness; heat accelerates drying damage.
Embroidery, sequins, beads, and appliqués: adhesive backs may dissolve, and metal components can corrode or detach under hot wash cycles.
Electronics and battery‑powered devices (headphones, hairbrushes with electronic components): exposure to water and heat risks short‑circuiting and battery rupture.
Hair‑care tools with plastic handles (combs, brushes, clips): high temperatures can warp plastic, weaken springs, and cause brittleness.
Infants’ clothing and blankets labeled “cold‑wash only”: manufacturers specify low‑temperature cycles to protect skin‑sensitive fabrics and maintain flame‑retardant treatments.
Items with attached adhesives (stick‑on patches, Velcro strips): heat softens glue, causing detachment and residue.

For items that cannot be laundered at lethal temperatures, alternative decontamination methods include sealed‑container heat treatment (e.g., a dryer set to high for 30 minutes), freezing at –4 °F (–20 °C) for at least 48 hours, or chemical treatments approved for the specific material. Each approach should be matched to the item’s material tolerance to avoid damage while ensuring lice eradication.

Preventing Re-infestation Through Laundry Practices

Treating Non-Washable Items

Bagging and Isolation Techniques

Lice and their eggs (nits) are eliminated when laundering reaches temperatures that denature proteins and disrupt cellular membranes. Empirical data indicate that exposure to water at 130 °F (54 °C) for at least ten minutes reliably kills both adult insects and viable eggs. Temperatures below this threshold may reduce viability but do not guarantee complete eradication.

Bagging involves sealing contaminated garments or linens in impermeable polyethylene bags before washing. The sealed environment prevents lice from escaping during handling and ensures that the thermal load is applied uniformly. When the bagged items are placed directly into a washing machine set to the lethal temperature range, the heat penetrates the bag material, maintaining the required temperature throughout the load.

Isolation refers to separating infested items from non‑infested laundry and processing them in dedicated cycles. This prevents cross‑contamination and allows precise control of wash parameters. Isolated loads can be monitored for temperature compliance, and any residual moisture can be dried at high heat to reinforce mortality.

Practical implementation:

Place infested textiles in heavy‑duty, sealable plastic bags rated for high temperatures.
Set washing machine to a minimum of 130 °F (54 °C) and select a cycle lasting ten minutes or longer.
Run isolated cycles for contaminated items only; avoid mixing with clean laundry.
After washing, tumble‑dry at 140 °F (60 °C) for at least 20 minutes to ensure residual eggs are destroyed.
Inspect bags for damage before use; replace any compromised containers to maintain isolation integrity.

Alternative Disinfection Methods

Lice and their eggs are typically eradicated in laundry when the water reaches a temperature that destroys their proteins. When that heat level cannot be achieved, alternative disinfection methods provide reliable control.

Chemical agents – laundry detergents containing permethrin or pyrethrins, when used at the recommended concentration, penetrate fabric and kill both adult insects and eggs within minutes.
Steam treatment – exposure to saturated steam at 100 °C for at least five minutes denatures the exoskeleton and eliminates nits without altering garment color.
Freezing – placing infested items in a freezer at –20 °C for a minimum of 24 hours disrupts cellular function and leads to mortality of lice and nits.
Ozone immersion – aqueous ozone at a concentration of 2 ppm for 30 minutes oxidizes biological membranes, providing a non‑thermal option for delicate fabrics.
Ultraviolet radiation – UV‑C light at 254 nm applied for 10 minutes destroys DNA in lice and eggs, suitable for hard surfaces and small garments.

Each method requires adherence to manufacturer guidelines and safety precautions. Combining two approaches, such as steam followed by a chemical rinse, enhances efficacy and reduces the risk of survivor populations.

Regular Cleaning and Maintenance

Bedding and Clothing Routines

Lice and their eggs are eliminated when laundering water reaches at least 130 °F (54 °C). Many health agencies recommend 140 °F (60 °C) to ensure complete mortality, especially for dense fabrics.

Effective laundering routine for bedding and clothing includes:

Wash items at 130 °F (54 °C) or higher; use a calibrated thermostat if possible.
Follow the wash cycle with a high‑heat dryer setting for a minimum of 20 minutes.
For fabrics that cannot withstand high temperatures, place them in a sealed plastic bag for 48 hours before washing; the lack of oxygen reduces viability.
Immediately store cleaned linens in a clean, dry environment to prevent re‑infestation.

Regularly laundering sheets, pillowcases, pajamas, socks, and undergarments at the specified temperatures interrupts the life cycle of head‑lice and prevents egg hatching. Consistency in these practices maintains a lice‑free household.

Vacuuming and Surface Cleaning

Vacuuming and surface cleaning are essential components of an effective lice eradication strategy. A high‑efficiency vacuum removes live insects and shed eggs from carpets, upholstery, and floor seams, preventing re‑infestation after laundering. The suction eliminates hidden reservoirs that washing alone cannot reach.

Laundering at temperatures of at least 130 °F (54 °C) for a minimum of ten minutes reliably kills both adult lice and their eggs. When clothing, bedding, or removable covers cannot be subjected to this heat, thorough vacuuming and disinfecting of the surrounding environment become critical. Combining high‑temperature washing with meticulous dry‑cleaning of surfaces reduces the likelihood of survivors.

Key actions for integrated control:

Vacuum all fabric‑covered furnishings, focusing on seams, tufts, and crevices; discard vacuum bags or clean canisters after use.
Wipe hard surfaces (tables, door handles, toys) with a solution containing at least 0.5 % hydrogen peroxide or a bleach dilution of 1 : 10.
Launder washable items at ≥130 °F for ≥10 minutes; for items that cannot tolerate heat, place them in a sealed plastic bag for two weeks to starve any remaining eggs.
Repeat vacuuming and surface disinfection daily for one week, then every other day for an additional week to address any newly hatched nits.

By maintaining rigorous vacuuming and surface sanitation alongside proper laundering temperatures, the complete life cycle of the parasite is interrupted, ensuring long‑term elimination.