Hello, Liquid filled blisters on penis commonly are indicative of pearly penile papules that generally go away by themselves and are harmless. They can also be caused by infected hair shaft, balanitis or genital dermatitis herpetiformis. DH, is an inflammatory cutaneous disease which is very itchy with a chronic relapsing course. It is not contagious. Take care of your hygiene and diet. If you are gluten sensitive, avoid food containing gluten. Take more vegetarian food. Take bath daily. Change your clothes everyday. Prefer wearing soft cotton clothes. You can apply hydrocortisone cream on the area affected to reduce itchiness. you can take a course of oral antihistamines to ease discomfort. It is good to know that your STD and herpes tests came clear. You are suggested to get clinically examined by a dermatologist, get required investigations done. You may be recommended laser therapy / treatment. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician