According to a publication by Texas A&M University, flea bites can cause small, red bumps that itch 12 to 24 hours after a bite and last a week or more. The length of time depends on a person's allergic reaction to the flea bite.
Scratching insect bites can lead to infections. Children's Health Network advises the use of calamine lotion or baking soda paste to relieve itching. If the bites are very itchy, applying over-the-counter 1 percent hydrocortisone cream four times a day can help. Fleas are often found on dogs or cats. To prevent flea bites, make sure that pets are free from fleas. Pet owners can remove fleas manually and apply flea powder or soap to their animals.