DS3 has severe ashtma and it can be really easily set off by aerosols. When this girl came over to stay last time we specifically asked her not to spray anything. She used an aerosol in the bathroom (which DS3 used straight after not realising) and then sprayed perfume all over downstairs. DS3 had a massive ashtma attack and we ended up having to take him to a&e that morning as soon as she left because we couldn't calm the breathing. She recently asked DS1 if she could stay again (a few of them are having a shopping weekend and she's not local). I'd said absolutely no and DS1 told her she couldn't. She's not happy about it (especially as another girl who asked ages ago is staying) Am I being completely unreasonable not letting her stay? And should I tell her the real reason why?