Check this test from choonster. Might be just what you need (should work for 1.10/1.11 but it's 1.12 branch): https://github.com/Choonster-Minecraft-Mods/TestMod3/blob/1.12.2/src/main/java/choonster/testmod3/item/ItemArmourPotionEffect.java. Also check the Forge LivingEquipmentChangeEvent for 1.12 (I don't know if it exists for 1.10). HTH.