Welcome to HCM.
Skin condition of your boy friend needs a close evaluation by a dermatologist
It is not like psoriasis
or any aggressive type of skin disease, so no need to worry more. Your skin condition might be Acrokeratosis verruciformis of Hoff, Acanthosis nigricans
or some other similar skin disease. It is not related to any food.
It needs some keratolyic agent like Lacticare lotion to apply.