After a flea bites, skin in the area immediately rises (wheals). The wheal fades in a few hours. Within 24 hours, an itchy papule (welt) appears. It begins waning after 48-72 hours, and is completely gone within a week. Scratching a flea bite will delay the healing time.
Immediate Reactions: 2-4 hours
Whealing occurs immediately after a flea bites. A wheal is an area of elevated skin that’s sometimes surrounded by reddening. The reaction is slightly itchy, but it fades quickly and doesn’t cause much irritation. The inflammation peaks within a few hours, and is completely gone 12 hours later.
Delayed Reactions: 2-7 days
A papule replaces the wheal 12 to 24 hours after the bite. A papule is a hard, raised bump. It can be red and swollen. Papules are extremely itchy, reaching their maximum intensity 24 hours following the bite. Papules begin waning on day two, and are often barely recognizable by the third day. Sometimes the lesion persists for 2 weeks. After fading, a pale red mark remains for around a week.
Occasionally, allergic individuals experience a more extreme delayed reaction. In these cases, blisters (bullae) form on the second or third days. The reaction peaks 72 hours after the bite.
Secondary Infections: 4-6 weeks
Rubbing flea bites can re-trigger whealing and extend the healing time. Scratching the lesions can break open skin, release fluid, and cause crusting. This frequently leads to a secondary infection. When a flea bite gets infected, the lesion fills with pus and takes the form of a pustule or boil. The infection heals over 4 to 6 weeks, but skin remains discolored for longer.
Rare Circumstances: up to 2 years
Some individuals are more sensitive to flea bites than others. Bites typically only persist for a few days. However, sometimes they last for weeks or months. In rare cases, there can be a prolonged effect that lasts a year or two. These bites are sometimes misdiagnosed as benign or cancerous lesions.
Other individuals, who are regularly exposed to fleas, may not react at all to the bites. Those with immunity only see a slight reddening of the skin, and this fades within a few minutes. However, the red puncture mark lasts for 3 to 4 days.