A dense, small granular rash may be caused by measles, chicken pox, scarlet fever, folliculitis, keratosis pilaris, and so on. 1. Measles: If the rash is caused by measles virus infection, a dense, small granular rash will also appear. 2. Chickenpox: The rash is caused by varicella-zoster virus infection, which can also appear as a dense, small, granular rash. 3. Scarlet fever: The rash appears because the skin is infected by group A beta streptococcus bacteria, which causes inflammation of the skin. 4. Folliculitis: an infectious disease caused by fungal or bacterial infection of the skin follicles, often manifested as red pimples, but also densely packed small granular rash. 5. Keratosis pilaris: mostly related to heredity, clinically manifested as a dense distribution of follicular pimples, there will also be a dense small granular rash. There may be other reasons for the phenomenon of dense small granular rash, please go to the hospital in time to check, follow the doctor’s instructions reasonable treatment.