Thanks for the query.
There could be multiple reasons to your clinical condition.
Its difficult to opine with accuracy with limited information.
It probably could be either a contact allergy, that is the most common scenario.
Treatment with antihistamines may alter the morphology and it may become difficult to diagnose. So consult a dermatologist and he will diagnose it for you and start you on appropriate medications. In case you are not in immediate access to a Dermatologist, you may consider taking a OTC antiallergic medications for relief.
Dr MK Agarwala