Peroxide/pəˈrɑːksaɪd/ Definition 1 of 2Pro Tip 1/3First Aid Usage Peroxide is commonly associated with first aid to prevent infection. Don't forget to put some peroxide on that cut. Pro Tip 2/3Hair Bleaching Peroxide is used in salons and products for bleaching hair. Adding peroxide to your hair will make it lighter. Pro Tip 3/3Handling with Care Use peroxide with caution as it can irritate skin and eyes. She wore gloves when applying peroxide.