Do flea bites blister?


Flea bites can blister. However, this isn’t the common skin reaction. Typically flea bites develop as hard, itchy papules (welts).


Insect Bites & Blisters

The bites of many blood-feeding arthropods can cause bullous (blister-like) reactions. Some of these parasites include fleas, bed bugs, ticks, mosquitoes, and kissing bugs. Of the possible culprits, fleas are most likely to cause a blistery bite, especially on legs.

Bullous eruptions sometimes seem to appear spontaneously, leaving the sufferer unaware of the cause. Insect bites are frequently the reason for the reaction. However, those afflicted may not realize they’ve been bitten, and this makes diagnosis difficult.

Reactions to Flea Bites

Flea bites can vary in intensity, depending upon a person’s individual response and level of sensitization. The bite reaction may manifest as whealing (raised skin), itchy papules (hard bumps), vesicles (numerous small blisters), or bullae (large blisters).

Common Reaction: Papules

The most common lesion associated with flea bites is a papule (hard bump). They typically appear in groups and are extremely itchy. Papules are a delayed reaction to the bite, occurring 12-24 hours after a flea has fed. Papules may develop a small central vesicle within 1-3 days.

Severe Reactions: Blisters & Vesicles

Bullous Eruptions

Occasionally, in extreme cases, flea bites take the form of large, red, irregular-shaped blisters. Bullous eruptions are delayed reactions which occur 48-72 hours after the bite. The reaction peaks at 72 hours.

An allergic response causes fluid to accumulate beneath skin in numerous, small, fluid-filled sacs called vesicles. With time, these vesicles merge together to form larger blisters (bullae). The tense blisters appear translucent or red, and there may be accompanying redness at their base. The blisters measure 3-6 mm in diameter. The reactions look similar to those seen with bullous pemphigoid, bullous impetigo, and linear IgA disease. It’s not uncommon for the blistered skin to die (epidermal necrosis).

Individuals at Greater Risk

Extreme reactions to insect bites are more common for children than adults. People with HIV, hematopoietic malignancy, or chronic lymphocytic leukemia are also more likely to experience a severe bite response.

Treating Blisters from Insect Bites

To treat bullous insect bites, the recommended course of action is to: 1) Drain the blister. 2) Relieve the itching by applying a hydrocortisone cream and taking an antihistamine. 3) In severe cases, systemic corticosteroids may be required.


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  • cindy September 22, 2016, 8:35 am

    my grandson gets the same bits all the time and they seem to swell up red and blestery i dont have a dog or cat or bed bugs i dont see spiders either in any thing here what can it be but he has been itcy though

    • Adam Retzer September 23, 2016, 2:39 pm

      Hello Cindy. Based on your description, it doesn’t sound like these bites and skin reactions are from fleas. Blistery reactions may be caused by another biting insect, allergies, poison ivy, infections, or other skin condition.

  • Sue October 20, 2016, 11:45 pm

    Hi..I suffer terribly from the most server reaction to fleas.
    Blisters hang of my ankles if I don’t drain them quick enough.
    This reaction started after I had Graves disease.
    I’ve been to skin specialists and doctors and no one can help with a resolution to this. It’s a constant battle everyone I enter a house with pets. And new ideas?

    • Adam Retzer October 21, 2016, 5:08 pm

      Hello Sue, that sounds like a pain to deal with. The only suggestion I can think of is to tuck your pant legs into your socks when you enter a home with a pet. Fleas can’t bite through most fabrics.

  • Angelina July 9, 2017, 9:18 pm

    My sister’s place has fleas from stray cats so whenever I visit, I leave with 1-3 bites..they’re usually just the small red bump that’s itchy, but this time it was a larger bump that I knew had pus inside. I ended up draining the blister/pus which was originally a clear bump but now it’s a smaller red bump that looks like it needs to be drained again. What do I do?

    • Adam Retzer July 30, 2017, 2:00 pm

      If it’s a severe reaction, I’d recommend seeing a dermatologist. If it’s a mild secondary infection, it will likely heal on it’s own in time.

  • Breanna Marquez October 30, 2017, 2:01 pm

    I think I got bit by fleas , I have a lot of tiny bumps on my forearm about 30 of them. When I wake up it looks as if there gone then when I scratch they all reappear and it looks like it’s spreading , what can I do I’ve had them now for 2 weeks.

    • Adam Retzer October 31, 2017, 12:56 pm

      Breanna, it’s possible those are flea bites, but it doesn’t sound especially characteristic of fleas. If you haven’t found any fleas in your home, then they probably aren’t flea bites. You may want to consider getting a flea trap to be certain there aren’t fleas in your house.

      It sounds more like some kind of allergic reaction (hives?). It may be a good idea to go see a physician in person so they can diagnose whatever the skin reaction is and where it comes from.

  • Deanna December 28, 2017, 2:11 pm

    Hi, my dogs have recently gotten fleas and they continue to get worse so we are working on getting rid of them. But i was recently bit by one in the neck and now the bite has swelled up and it feels like there’s a knot in my neck. It’s making my entire neck ache. I’ve drained the pus from the bite but my neck is killing me. Any if it’s a side effect?

    • Adam Retzer December 28, 2017, 4:56 pm

      Your situation sounds somewhat usual and severe with your whole neck aching. Flea bites don’t normally contain pus. However, if the bites are scratched, it can create an open sore and introduce bacteria into the bite. Then it may get infected and fill with pus. Whether your lesion is an infected flea bite or something else, it sounds like you have an infection and should consider seeing a physician.