Hello,
A rash which spreads and present all over the body can be a viral rash or drug allergy. One of the most common ones is an allergic reaction or contact dermatitis. It can happen to chemicals, wool, soaps, cosmetics and certain foods can cause itchy skin. You can take some OTC oral antihistamine medications like Benadryl or Claritin and see if it helps.
For mild-moderate symptoms a weak steroid may be used (e.g. hydrocortisone as dermacort), whilst more severe cases require a higher-potency steroid (e.g. clobetasol propionate, fluocinonide).But they are available under prescription and should be taken only after consulting a dermatologist. Also use mild soaps and wear cotton clothes.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
There are a number of different conditions that can cause a rash like you describe. Certainly a reaction to a new medication can do it, but so can eczema, psoriasis, pityriasis rosea and scabies.
Scabies, for example, presents as small, very itchy bumps with a linear scale on top. It is caused by a mite that is too small to see with the naked eye but is seen under the microscope when one of those lesions is scraped with a blade and mineral oil. Scabies can spread anywhere on the body but particularly likes spaces between fingers and toes, the wrists, underarms, groin, buttocks.
These disorders are treated differently, so I recommend a consultation with a board-certified dermatologist for a more definitive diagnosis and treatment.
Disclaimer: Dr. Emily Altman and Advanced Skin Wisdom provides the content on this website solely for informational and educational purposes. Information provided on this website should not be considered medical advice and is not a substitute for consultation with a qualified medical professional. Communications to or from Dr. Altman and Advanced Skin Wisdom and any person will not be considered to establish a patient/doctor relationship.