If there are many bumps on the neck, they may be flat warts, filiform warts or skin tags if there are no conscious symptoms. Flat warts and warts are caused by human papillomavirus infections, and the rash can increase when you rub or scratch in the shower. The rash is rough and hard due to HPV infection, while the skin is soft and smooth, usually in the folds and obese people, but also in the armpits, which can be treated with ion cautery or liquid nitrogen freezing. If the rash has a central umbilical pit and increases after bathing, it may also be a viral infection that causes infectious molluscum contagiosum, which needs to be scraped for treatment. If the rash itches significantly, consider the possibility of allergic disease, allergic disease rash is red papules, may have oozing, treatment is mainly given to anti-allergic treatment.