The spots you describe may be due to an allergic reaction, a fungal infection, or a temporary skin condition such as hives. Since they come and go on their own, they are often harmless, but avoid scratching to prevent infection. You may use a gentle, fragrance-free soap and apply a mild over-the-counter antihistamine cream or calamine lotion to reduce itching. If the spots become persistent, widespread, painful, or are accompanied by other unusual symptoms, please consult a doctor or dermatologist for proper diagnosis and treatment.