The most common causes of such recurrent rashes are:
Atopic dermatitis: this is a type of eczema. It consists of an itchy red rash which can be found anywhere in the body. Cause is usually due to an allergen which is recurrent in the environment. But often no such cause can be found.
Scabies: scabies is due to infestation by mites. You need antiscabies treatment for this.
Granuloma annulare: this causes recurrent bumps which are often in a ring formation, cause is unknown.
Lichen planus: this gives rise to itchy purple or reddish coloured flat bumps, cause is believed to be immunological.
Psoriasis: gives rise to itchy red rash associated with silvery scale like patches. cause is believed to be immunological.
For you the most likely is Atopic dermatitis. This is often provoked by exposure to some allergen. You need to pay careful attention to your environment to see if you can find out any allergen which could be the cause.
Insect bites are a possibility. Mosquite, horsefly, ticks, midge or gnats, fireants, chiggers, etc can cause such reactions. It could also be related to certain medicines, foods, suppments, etc. Check out whether there is any medication associated with the rash. . Also try to recall any associated foods, specially foods like nuts, some new types of meat, fish, etc before these recurrences. You could be having a food allergy. You should also watch out for any soaps or detergents. Also try to recall any activities associated with this, like hiking to some place, cleaning the house or some area of the house, some hobby like wood working etc which coincide with the rashes.
If you find anything which could have caused the allergy, then you have to avoid it. However, quite as often, no definite cause of such allergic reactions can be found, do not worry if this is so. Most of the time, cause for Atopic dermatitis is not detected.
You should take an antihistaminic like Cap. Claritin (OTC) one capsule daily. Also apply 1% Hydrocortisone ointment. This will get rid of the rash.
However, if the rashes keep recurring, you should see a doctor. Other causes like scabies may be implicated.
Hope I have been able to clarify the situation for you and helped in resolving your query.
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