Since you have been using antifungal treatments for 5 years without success, it is likely that the underlying cause is not a simple fungal infection or that the infection has become resistant. Both you and your son should consult a dermatologist to rule out other conditions, such as scabies, chronic eczema, or a persistent bacterial infection. It is important to avoid self-treatment and undergo appropriate tests, such as skin scrapings or a biopsy, to reach an accurate diagnosis and receive targeted treatment.