Thanks for your query
You seem to be developing an allergic skin reaction.
considering the sites involved in your case, possibility of a photosensitive rash
which is a sun induced rash can be considered.
Avoid prolonged sun exposure.
use a sunscreen regularly with spf of atleast 26.
Wear cotton clothes.
Wear full sleeved shirts in order to avoid direct sun light.
Apply a topical steroid
cream over the area twice a day for 3 to five days.
Can take oral antihistamines for itching.
Hope it helps
dr geetika Paul