This recurring issue could be a pilonidal cyst or hidradenitis suppurativa, both of which are common and highly treatable. Since you have a sulfur allergy, sulfa-based antibiotics must be avoided. Instead, a doctor may prescribe non-sulfur alternatives such as oral cephalexin, doxycycline, or topical clindamycin. To manage it daily, try applying warm compresses and washing the area with generic benzoyl peroxide or chlorhexidine cleanser. Because this is recurring, antibiotics alone may only offer temporary relief. I highly recommend visiting a doctor or dermatologist, as these conditions often require a minor clinical evaluation or procedure to resolve completely and permanently.