What causes a bump on a dog after a tick bite? - briefly
The swelling usually results from a localized inflammatory response to the tick’s saliva, which can progress to a granuloma or secondary infection such as Lyme disease.
What causes a bump on a dog after a tick bite? - in detail
A swelling that appears after a tick has attached to a dog is typically the result of the animal’s immune reaction to the parasite’s saliva. The bite introduces proteins that prevent blood clotting and suppress inflammation, allowing the tick to feed for several days. The host’s immune system recognizes these foreign proteins and releases histamine and other mediators, producing a localized, raised lesion.
Common mechanisms include:
- Local inflammatory response – histamine‑driven edema and redness develop within hours to days.
- Secondary bacterial infection – the mouthparts of the tick can carry bacteria such as Staphylococcus spp. or Bartonella, leading to pus‑filled abscesses if the skin barrier is breached.
- Allergic hypersensitivity – some dogs exhibit a heightened IgE‑mediated reaction, resulting in larger, more persistent bumps.
- Tick‑borne disease manifestation – pathogens like Borrelia burgdorferi (Lyme disease) or Ehrlichia spp. may cause granulomatous nodules or panniculitis as the infection progresses.
Evaluation should consider the size, duration, and characteristics of the lesion. A firm, non‑fluctuating nodule persisting beyond two weeks often warrants cytology or biopsy to rule out granuloma formation. Rapidly enlarging, painful, or pus‑filled swellings suggest bacterial involvement and may require antimicrobial therapy.
Prevention focuses on regular tick checks, use of approved acaricides, and prompt removal of attached ticks with fine‑pointed tweezers, minimizing the duration of saliva exposure and reducing the likelihood of an abnormal bump forming.