Bumps can appear on your skin in an amazing variety of sizes, shapes and colors. Most of them are harmless, but some might itch or otherwise be annoying. Few are dangerous. Bumps can form patterns and can be on just one area of your body or break out almost everywhere. Your bumps may be unusual and only your doctor can tell for sure what they are. If they don't go away or keep coming back, that is who you need to see.
Folliculitis
As pictured in the textbook "Clinical Dermatology", the lesions that are most common at about a distance of 1/4 inch are forms of folliculitis. This is an inflammation or infection of the hair follicles. The hair follicles are close together, but usually only some develop the problem. If these are all in the same area, the bumps may be about this distance apart. In folliculitis, bumps are usually red. A pimple is a form of folliculitis.
Causes
Your hair follicles provide an opening for germs to enter and multiply. Most folliculitis is an infection. Staphylococcus bacteria are responsible for many of these infections. Pseudomonas aeruginosa bacteria can cause a specific type of folliculitis called hot tub folliculitis. The CDC explains that this happens when the bacteria is shed into the warm water and the hot tub or pool has not been cleaned and treated adequately. These bumps do not always require treatment. The lesions from this cause are sometimes in a line where the elastic in swimming suits traps the water close to the skin.
Pseudofolliculitis
Some hair follicle bumps are not infections, but bumps from a hair twisting and re-entering the hair shaft. This is more common in some individuals and with curly hair. A number of follicles in the same area are usually involved. The face and nape of the neck where hair is shaved are common locations according to DermNet NZ. This condition is called pseudofolliculitis, or false folliculitis. The bumps are caused by a foreign body reaction to the hair.
Keloids
Some forms of folliculitis can eventually cause keloids in people who are prone to them. This results in permanent bumps that are not red. Keratosis pilaris is another condition with bumps close together and is often seen on the front of the thighs. The friction from clothing and scratching the bumps can keep this condition active for years. The bumps can become infected, and usually, at least some of them are red.
Other Bumps
Other skin conditions that can appear about 1/4 inch apart are herpes virus infections, which are fluid-filled blister-like bumps, and papilloma virus infections. The papilloma virus causes warts, and some will appear in groups. Many skin conditions begin with bumps that are separate and distinct but that then change and merge or flatten or enlarge. It is safest to have your bumps diagnosed, especially if you are not feeling well or the bumps change.
References
- "Clinical Dermatology" Third Edition; Thomas P. Habif, M.D.; 1996
- CDC: Hot Tub Rash (Pseudomonas Dermatitis/Folliculitis)
- DermNet NZ: Pseudofolliculitis Barbae
