Dear saleha.sarfraz ji
The allergens that come to your notice must be avoided for the time being. Ayurveda recommends to build bodily resistance in the form of immunity to prevent such rashes. Here the role of blood purifying herbs is very good.
I would recommend you to have Haridra KHand 500mg. Tab. Allerin 1 , tab. Gandhak rasayan1 TDS.
and spicy food.