Dry Skin

Dry Skin causes several effects:

Game descriptions

Diamond, Pearl, Platinum, HeartGold, SoulSilver:Reduces HP if it is hot. Water restores HP.
Black, White, Black 2, White 2:Reduces HP if it is hot. Water restores HP.
X, Y, O.Ruby, A.Sapphire:Reduces HP if it’s hot. Water restores HP.
Sun, Moon:Restores HP in rain or when hit by Water-type moves. Reduces HP in sunshine, and increases the damage received from Fire-type moves.
Ultra Sun, Ultra Moon:Restores HP in rain or when hit by Water-type moves. Reduces HP in harsh sunlight, and increases the damage received from Fire-type moves.
Sword, Shield, B.Diamond, S.Pearl:Restores HP in rain or when hit by Water-type moves. Reduces HP in harsh sunlight, and increases the damage received from Fire-type moves.
Scarlet, Violet:Restores the Pokémon’s HP in rain or when it is hit by Water-type moves. Reduces HP in harsh sunlight, and increases the damage received from Fire-type moves.