When AD begins after your 18th birthday, dermatologists call it adult-onset atopic dermatitis. You'd receive this diagnosis if you never had AD before. A peak.
The Journal of Allergy and Clinical Immunology talks about adult-onset eczema: a common and poorly understood problem.
Adult-onset atopic dermatitis is still an under recognized condition as there are only few studies regarding this entity. As compared to childhood onset atopic.