Hello and welcome to HCM.
Thanks for putting up your question over here.
From your description it seems you have urticarial rash,a form of
allergic reaction.
This allergic reaction can be to any food,chemicals,medicines,heat,moisture.You need to observe what exactly started it so that you can avoid further exposure to that factor.
If I were your treating doctor ,I recommend,
-Oral anti histaminics like
cetrizine or
loratidine once a day .
-Local application of
hydrocortisone cream(prescription drug) for 3-4 days, ice pack application may give some relief.
Aloe vera/calamine lotion can be applied 3 times a day at the itchy site.
Dont scratch the rash.
-Wear loose and light cotton clothing.Apply talc at sites where you sweat the most.
If the symptoms persists or worsens,visit to physician.Option of oral
prednisolone in decreasing doses may be considered.
Hope this information helps.
Thanks.