This is likely to be due to an allergic reaction.
Check out whether you have started any new medications. Also try to recall any new foods that you took, specially foods like nuts, some new types of meat, fish, etc. You could be having a food allergy. You should also watch out for any new soaps or detergents.
It could also be an allergic reaction to an insect bite.
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.
Meanwhile take Cap. Claritin (OTC) 1 cap. daily, this will cure the itching and rash. Also apply 1% Hydrocortisone cream (available OTC) on the rash and itching.
You should get immediate relief from the itching and it should heal within two - three days.
However, if itching or rash persists or it gets worse, see your doctor or go to the ER.
Other dermatological conditions like scabies, eczema, etc, need to be ruled out - your doctor can also prescribe prescription strength anti histaminics.
Try with the Claritin and ointment first.
Take care - this is likely to be an allergic reaction - try with the Claritin - if it persists see a doctor.
Take care - wish you good health and a quick recovery. Stay safe.
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Dr. P. Jyoti, MD.