My 2+ year old has been having running nose for at least 3 mths. he has bouts of insect bite or rashes i can't differentiate. how to diagnose & cure?

Allergies: I suspect it's allergies. If it's clear drainage and if he has associated allergy symptoms like sneezing, red itchy eyes then allergic rhinitis is likely the cause of his runny nose. If you haven't seen an insect bite him and in particular if this is a recurrent rash it's unlikely to be an insect bite. Eczema or allergic dermatitis are commonly associated conditions. See your pediatrician.

ALLERGIC RHINITIS ?: He needs to see md to find out the cause of the rashes and environmental control of possible causes of his chronic rhinitis.