Hello there, Welcome to healthcaremagic. I understand your problem.There are lot of reasons which can cause vaginal itching like bacterial,fungal,chemical substances.In your case as you have described you get it after using the sanitary napkin,i think the trigger is the napkin itself. Try changing the present sanitary napkin and change your napkins within 3-4 hours or before that if needed.You can use any antifungal cream or ornidazole gel in the vaginal area to get relief.You should also follow these to help prevent infection; 1.Keep your vaginal area clean. Use mild, unscented soap and water. Rinse well. 2.After using the toilet, wipe from front to back to avoid spreading yeast or bacteria from your anus to the vagina or urinary tract. 3.Wear underwear that helps keep your genital area dry and doesn t hold in warmth and moisture. One good choice is cotton underwear. 4.Avoid tight-fitting clothing, such as panty hose, and tight-fitting jeans. These may increase body heat and moisture in your genital area. 5.Change out of a wet swimsuit right away. Wearing a wet swimsuit for many hours may keep your genital area warm and moist. 6.Change pads or tampons often. 7.Don t douche or use deodorant tampons or feminine sprays, powders, or perfumes. These items can change the normal balance of organisms in your vagina. Hope i could help you.Take care