Help!

Me and my boyfriend have sex fairly often. But lately we've had to slow down because he's getting scabs right under the head of his penis. And when they fall off the skin is really irritated. We'll for it to heal but as soon as we do it it gets all swelled up and red and the process starts all over again. Doesn't matter if we have sex vaginally or I blow him, it's always irritated after. Any idea what this could be ?