The sudden itchiness of flat warts may be a normal symptom of the disease, or it may be caused by skin allergies and other reasons. 1. Normal symptoms: flat warts usually have no conscious symptoms, occasionally mild itching, so flat warts suddenly become itchy may be a normal symptom of the disease. 2. Skin allergy: if skin contact allergens caused by skin allergy, the damaged skin stimulation, it is likely to cause flat warts at the itchy situation, but this itching and flat warts have no correlation, caused by allergies. If you’ve got a flat wart that suddenly becomes itchy and continues to be unrelieved, you should go to the regular hospital to find out the cause of the problem, and carry out the relevant treatment under the guidance of the doctor.