His body absorbed the slime on impact.

As usual, the slime monster used their standard tactic of just jumping at him, but instead of slashing it mid-air like he was used to doing, Link just stood there, wanting to see what the potion did. The monster attached to his body and tried restraining him, but in soon began sinking into his clothes, Link's skin absorbing the creature into it. Link watched as the bright blue blob disappeared inside of him, then felt a white-hot flash of pleasure burn through his body, starting in the areas the slime monster had touched, and then spreading everywhere else. Link lost himself in the ecstasy of that moment, and as he did so his body changed without him even noticing. His hair grew out a little longer, his torso slimmed down and became less bulky, and the muscles all over his body dwindled a little, replaced with softer flesh. When Link came down from that high, he didn't realize anything was different, aside from his equipment feeling a little heavier than usual.