How can i distinguish between ringworm and an allergic reaction?

Fungal forms: Good question. Specifically, allergic contact dermatitis can indeed look similar to tenia corporis. Also can resemble nummular eczema. Also, ringworm can itch and seem dry. A scraping of ringworm will often show signs of fungus under the microscope, but one can certainly do a formal biopsy. Steroid creams will make the itching of both better, but can make ringworm worse.