Pairs of Skin

Maggie, after scratching a scab this morning:

Maggie: Luckily I have another pair of skin!

Daddy: What?

M: I had another pair of skin under my scab, so it’s not bleeding.

D: Oh.

M: I have three pairs of skin.

D: Three? Pairs of skin?

M: Yes. If I scratch off one pair, then there’s another pair. If I scratch off that one, then there’s a third pair. But under the third pair is my blood.