Hello, I understand that your hands are itchy and form bumps. Whenever there is appearance of rash on any part of the body it is mainly due to allergy where there is involvement of the immune system. It causes itchiness as long as the object is in contact with the body. This condition is known as Contact Dermatitis. This could be due to various substances like Hair dye, nickel, leather, rubber, citrus fruit, medications, poison ivy and so on. Whenever there is damage to the skin it results in rash. It usually subsides in a day or two or it may result in blisters. Since you also mentioned that you wear a watch to school that could also result in contact dermatitis. I would suggest you to get a few investigations like skin patch test to find the source of allergy. You can take antihistaminic drugs like Cetirizine at bedtime after food for 3-4 days. If the symptoms worsen and it is associated with swelling, I would advise you to consult your dermatologist for immediate treatment. Hope this helps. Thank you.