There are several possibilities for red spots on the thighs: a. Pigmented purpura dermatosis, the cause of which is unclear, related to increased capillary permeability and extravasation of red blood cells; treatment can be oral levocetirizine hydrochloride capsules and topical dinaide ointment; b. Allergic purpura, mainly due to allergies, or bacterial, viral, fungal infections; treatment can be oral rutin tablets, calcium carbonate D3 tablets and vitamin C capsules, and topical application of Denide ointment; third, eczema, mainly caused by allergic factors, may be sun allergy or salt bath, milk bath and other habits; can take oral levocetirizine hydrochloride capsules, and topical application of mometasone furoate ointment for treatment.