Your veterinarian should be consulted as these organisms may be susceptible to only very specific antibiotics. Ringworm is a common fungal disease of the skin. It usually occurs in young or immunosuppressed dogs. Fungi are plant-like organisms that include such things as yeast, molds and mushrooms. Ringworm is usually characterized by red-ringed patches with broken hair shafts.
Ringworm can take many forms however.
Infected hair shafts will remain infectious for over a year so very thorough cleaning around infected animals is mandated. Hormonal diseases can also affect the skin. The skin may become dry and scaly. It may also become darkened in color. The hair may become thin, brittle or fall out completely.