SLASH'EM players should retain any holy wafer that they find. These are excellent items for lawful heroes, good for neutral heroes, but chaotic heroes must be careful with them.
Any player can eat a holy wafer to cure their sickness and lycanthropy. Lawful players will also heal by 20 to 39 HP. Chaotic players will lose 10 to 19 HP, but will not go below 1 HP.
Source code reference: src/eat.c#line2095, SLASH'EM 0.0.7E7F2