Generally, I would say it's no big deal. I really would.
On the other hand, in the past 5 years of being a mother (in my experience) there are 3 women whose kids are constantly ill. I've never seen their kids without some sort of sniffle, dribble, cough or worse...and yet they still insist on play dates.
I really (I know how this sounds) am a genuinely nice person. So when these women became more and more desperate for frequent play dates, If I had the time I would ALWAYS say yes. My son would ALWAYS get sick...and then I started getting sick too.
Other Mum asks for play date, my DS says 'No mommy, I don't want to' I make him go anyway.
Her child throws up, she has to turn around and go back home; I thought this was the end of it. I decide to continue to hang out with my family in the park. She comes back, her youngest vomits another 3 times; her other children are full of snot and coughing and sneezing. My DH see's this and decides to entertain the sick children to keep them from me. We get home and the whole family is vomiting and have the worst stomach bug+snotty+sneezy disease of our lives. Takes us 3 weeks to recover. In this time the mother doesn't take the hint that we're ill and can't schedule another play date. She gets pretty offended; I don't even mention that we caught an illness from them.
After some time (said 3 weeks) this woman demands another play date. DS implicitly says "NO NO NO!" DH says "No!" And I say "people get sick, they do--they still can't be sick after all these weeks". So play date happens, she brings her kids and ALL of them have a wet and chronic cough that once it starts wont stop till their mother hits them on the back...and even then it leaves the youngest two blue in the face because they can't manage to breathe.
I fall ill, go to GP he says "looks like bacterial pneumonia" he tests for it, comes back positive. Other mum calls to ask if we'd like another play dateDoctor tells me I need to be admitted to the hospital because there is too much mucus in my lungs. I tell this woman, look...I've got Bacterial PneumoniaI don't know where I've got it from but I'm seriously ill. I'll get in touch when I'm better. She instantly sends long winded messages about how I don't even hug her children so I couldn't have got anything from them...and that they aren't sick. She texts the next following days saying "I went to GP, my kids don't have bacterial pneumonia. So I don't know where you got it from, it wasn't us."
Like I said, I'm super nice so I didn't accuse her of anything.
At this point, I'm done. It wasn't even the illness that put me off, it was the sheer bullying nature of the text messages.
I do think she's a nice woman, and I genuinely love her kids; but I love my kids more.
*but if it's only happened once, then it's no big deal. I feel like if someone is a repeat offender then some scrutinization needs to happen.