I would be pleased to answer your posted query .
From your description of symptoms it looks like a Contact Dermatitis
. However , I would also suggest that you should get it examined to rule out Gram negative folliculitis
or cellulitis which is commonly acquired from the Hot Tubs .
You should book an appointment with the Dermatologist
. Apart from the anti histamines
that you have mentioned you might need to take an antibiotic and a better application lotion for your body .
Thanks and Take care .