How long does a tick swell? - briefly
A tick generally stays visibly enlarged for two to three days after it has fed, then it begins to shrink as digestion proceeds. Persistence of swelling beyond a week may signal infection or abnormal attachment.
How long does a tick swell? - in detail
Ticks enlarge rapidly after attaching to a host because they ingest blood. The visible swelling, known as engorgement, follows a predictable timeline that varies with species, life stage, and temperature.
During the feeding process, a tick progresses through three phases:
- Attachment (0–12 hours): The mouthparts embed, and the body shows little change. Slight reddening may appear around the bite site.
- Rapid expansion (12–48 hours): Blood intake accelerates. Most species increase in size by 2–3 times within the first 24 hours and reach near‑maximum volume by 48 hours.
- Full engorgement (48–96 hours): The tick’s abdomen becomes markedly distended, often appearing balloon‑like. For adult females of Ixodes scapularis and Dermacentor variabilis, full swelling typically occurs between 72 and 96 hours. Male ticks and nymphs usually complete engorgement earlier, often by 48 hours.
Environmental temperature influences the rate of development. Warmer conditions (≥25 °C) can shorten each phase by 10–20 percent, while cooler environments (<15 °C) may extend the feeding period up to 120 hours before full swelling is evident.
After detaching, the engorged tick shrinks as it digests the blood meal. Visible reduction begins within 24 hours and may continue for several days, returning to its pre‑feeding size after the exoskeleton hardens.
Key points for practitioners:
- Expect noticeable enlargement to start after the first half‑day of attachment.
- Full swelling generally appears between three and four days for adult females; nymphs and males often complete the process within two days.
- Temperature and host species modulate the timeline but do not fundamentally alter the sequence of phases.