Hello,
I cannot confirm anything without examination but it can be due to contact dermatitis,eczema,heat rash or sweat dermatitis.
You can take non-sedating antihistamines such as Cetirizine or Loratadine(Claritin). Short courses of oral cortisone or steroids are taken for short periods (one to three days) to settle more severe symptoms.You may take Vitamin C along with the prescribed treatment. Vitamin C is a general anti-allergy supplement. Also apply calamine lotion and a mild steroid cream like dermacort on the rash.
In case the symptoms persist then pls consult a dermatologist.
I hope it helps.Take care and pls do keep me posted on how you are doing or if you have any additional queries.Kind regards
ADDITION : Now I'm starting to get pimples around my lips! Help?!