Hi,
This could be due to an allergic reaction called hives.Hives are red, itchy welts or swellings on the skin that often come in clusters which may simply look like large red circles.
Hives can appear anywhere on the body, cropping up either in one small area or covering large patches of skin. They most often occur as part of an allergic reaction. No one lesion lasts more than 24 hours, but new ones may continue to appear until the condition resolves.
Hives usually appear suddenly and go away on their own in a matter of days, hours, or even minutes. Chronic hives, however, can last for six weeks or more.
Foods (commonly eggs, shellfish, nuts, berries, dyes, or other additives) and drugs (any drug can touch off an allergic reaction, although allergies to penicillin, sulfa, and aspirin are especially common) are common causes of this outbreak.
Physical exertion or exercise, stress, illness, chemicals, cosmetics, textiles, and pressure from materials can also bring this on.
To soothe itchy skin, try cold compresses, calamine lotion or a cool shower. You can also take anti-histamines like Cetrizine to treate the rash.
Typically, chronic hives go away on their own, whether you treat them or not. About half of all chronic cases clear up within a year.
ref:http://www.myonlinewellness.com/topic/hivestreatment
Hi
Based on your post, the red bump appears to be solitary and is localized in only one area of the body. This suggests that an insect bite, a fungal infection, a bacterial infection may be likely here. This may rule out more generalized disease conditions such as a viral infection. Dermatitis may also be a differential as well as vascular insufficiencies. These are just differentials of course. Applying mildly potent corticosteroid cream like hydrocortisone 1% and moisturizing the area with a light vitamin cream may help.