Allen loves Link’s hair. He really like’s brushing it even though Cross used to make him brush his stupidly long hair. With Link it’s different (not to mention half the length)
Link cuts Allen’s hair for him. The exorcist never really paid attention to how his hair looked, as long as it sort of covered his scar, but after Link started cutting it, Allen realized how much nicer it feels when it’s well cut.
Once Link broke his wrist and wasn’t able to braid his hair. He put it up in a ponytail, but then Allen said he could braid it. It turns out he’s really good at doing long hair because Cross would make him too his hair.
Allen really really likes when Link scratches his head. They both learned his when Allen fell asleep on a train and ended up with his head on Link’s lap. While reading his book, Link started absently scratching Allen’s head and he basically started purring in his sleep. Blushing ensued and now Allen can’t even start to fall asleep unless Link scratches his head. He’s a little spoiled.
After having to flee the Order, Allen didn’t bother to cut his hair just because. After meeting up with Johnny and Kanda, he had intended to cut it, but he once he found out Link was ‘dead’, he couldn’t bring himself to cut it. He hopes it will soon be long enough to braid. He wonders if he’ll survive long enough for it to reach that length.