After being bitten by fleas, red papules (small red dots) will appear on the skin, mostly distributed in groups, which may be accompanied by itching, and in severe cases, blisters, maculopapules, erythema, purpura and other symptoms may appear. Fleas are parasites that survive by sucking the blood of their hosts and can parasitize humans, cats, dogs and other hosts. After sucking blood, fleas will form red dots, or erythematous papules, which are often distributed in clusters and may be accompanied by itching; blisters, maculopapules, erythema, purpura, and other symptoms may occur in some patients with severe allergic reactions. After being bitten by fleas, you can apply some topical anti-inflammatory and anti-itch medications such as mometasone furoate gel and butyl flufenamic acid ointment locally under the guidance of your doctor, and you can take antihistamines such as cetirizine and loratadine orally to stop the itching. It is recommended that people keep the environment ventilated and dry, take baths and change clothes diligently, and pay attention to the hygiene of pets to prevent flea bites.