Itchguard contains the active anti-fungal medication clotrimazole which is an effective topical treatment for ringworm (along with many other fungal skin infections). The darkened color of the skin where the ringworm was could be due to the inflammation caused by the infection. This is a known medical phenomenon called post-inflammatory hyperpigmentation . In any case, I usually tell my patients to continue using anti-fungal cream for at least a week after the symptoms resolve to make sure you have fully eradicated the fungal infection.