That's tissue inflammation.
It's a REACTION to your radiotherapy.
Breaking Bad Season 2, Episode 9
If the two of you engage in intercourse,
this will create the biochemical REACTION...
The Big Bang Theory Season 2, Episode 9
because, of course, this is an
exothermic REACTION, which means
Breaking Bad Season 5, Episode 14
No visible REACTION.
The Big Bang Theory Season 7, Episode 5