Flea bites don’t itch immediately. The lesion which appears right away isn’t too irritating and it fades quickly. However, 24 hours after the bite, a hard bump called a papule forms. Papules cause considerable itching.
Flea bites vary in severity. The reaction depends upon a person’s individual response, as well as their level of sensitization from previous exposure. Most people experience both an immediate and a delayed reaction. However, sometimes there’s no immediate reaction.
Immediate Reactions don’t Itch (much)
Within 5 to 30 minutes of a flea biting, skin at the location will rise. This is known as whealing. Wheals are slightly pruritic (itchy). However, these early lesions don’t usually bother people. Complaints are rare. The wheals aren’t too irritating and they fade away quickly. In fact, since fleas are small and hard to see, people may not be aware of being bitten until a day later.
Delayed Reactions Itch
24 hours after the bite, a new type of lesion arises, and skin in the area begins itching. The most common delayed reaction is a solid elevation of skin, known as papule. Papules are extremely itchy, especially at night. They cause the majority of complaints in health clinics. The severity of the irritation peaks within 12 to 24 hours. Children typically experience more intense reactions than adults.
It can be difficult to avoid scratching the itchy lesions. However, doing so often leads to secondary infections. And this often prolongs the irritation.
In extreme cases, fluid-filled blisters (bullae and vesicles) may form 48 to 72 hours after a flea has fed. These lesions also cause itchiness.