Fleas are bloodsucking parasites of birds and mammals in the order Siphonaptera. Adult fleas are wingless with their larvae being pale and caterpillar-like. Fleas can travel very far distances by jumping up to one hundred times their body length using their legs and a spring-like mechanism.

Only adult fleas feed on blood using their piercing mouthparts, while flea larvae feed on debris in bedding and in dust and lint debris in carpeting. Female fleas lay eggs in these areas that take two weeks to hatch into larvae. Fleas are surprisingly resilient, especially in their pupae stage where they can survive in severe environments for long periods of time without any food. Adult fleas have even been shown to live one or two months without a blood meal. Interestingly, fleas are stimulated to hatch when warm-blooded creatures enter their territory of protective cocoons, which explains why it is common for homes to be infested with hordes of fleas when new owners move in.

Flea bites are usually itchy, small papules arranged in a non-follicular pattern in groups of three, also known as the breakfast, lunch and dinner configuration. They usually occur around the feet and lower legs, as fleas tend to live in the carpets and floorboards. Flea bites can induce papular urticaria which is diagnostically made by clinical examination. Papular urticaria is a hypersensitivity disorder in which insect bites, usually those of fleas but often of mosquitoes and bedbugs, lead to recurrent and sometimes chronic itchy papules on exposed areas of skin, with large welts that are painful and hot to touch. Flea bites are easily infected as scratching can introduce bacteria into the open sores. Infected flea bites become painful, red, pussy and swollen. Flea allergy may cause respiratory symptoms in humans, especially in patients allergic to cats however anaphylaxis has not yet been reported.

Patients should be advised to never scratch the bites as fleas defecate when they feed, and scratching can irritate the skin and introduce bacteria deeper into the skin causing an infection. An oral antihistamine can help reduce the itching of the flea bites as well as lessen any allergic reactions experienced. Topical antihistamines and anti-bacterials, in addition to tepid baths with an oatmeal solution, will help to cleanse and soothe the skin when needed. Patients should avoid hot showers as the hot water can actually make the itching worse, and should make sure the house and yard are completely treated for fleas, especially larvae.

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