Greetings! its mostly not an infection - rather an irritant or allergic reaction to hair dye. Being ammonia free doesnt really make the dye safe or allergen free. Most dyes have a substance called PPD which is the implicated agent. Avoid regular dyes, there are some dyes - prescribed by the dermatologist which are PPD free and may be safe in your case. Kindly see a qualified dermatologist near you. YOu could send in your further queries to me on follow up messaging. Warm regards.