Ring-shaped skin lesions that slowly increase in size are most commonly caused by a fungal infection called Tinea corporis. Despite the name, it is not due to a worm but a fungus that affects the outer layer of the skin, leading to red, circular patches with clearer skin in the centre and itching. This condition spreads easily through sweat, close contact, or sharing towels and clothing. Treatment usually involves antifungal creams applied directly to the affected area for a few weeks, even after the rash starts improving, to fully clear the infection. In more widespread or stubborn cases, doctors may prescribe antifungal tablets. It is also important to keep the skin clean and dry, avoid tight or sweaty clothing, and not share personal items to prevent spreading or recurrence. Avoid using steroid creams without medical advice, as they can worsen the infection and make it harder to treat. If the patches continue to spread, become painful, or do not improve within a couple of weeks, it is best to consult a doctor for proper evaluation and treatment.