Keep an eye on it. Maybe congratulate her on always remembering to wash her hands but also make it clear that as my mother said, "we all got to eat our peck of dirt before we die."
Current thinking (maybe share this with her) is that we shouldn't live in too sanitised a world because if we do, we fail to allow our immune system to keep getting its regular microdoses of immune stimulants which are enough to stop it from going overboard and triggering things like asthma.
In other words, we NEED our sub-pathogenic doses of bacteria, our immune system needs to be getting gently triggered at regular intervals, to stop it from going into massive overdrive.
To continue to be safe, we need to be sensible. Hand-washing is good, using antibacterial soap etc is bad (unless you are cleaning a hospital operating theatre, of course). If you want to be safe at home then there are other, safer, things you can do. having those multi-coloured chopping boards for different purposes and using them accordingly is good; relying again on antibacterial wipes etc to compensate for poor kitchen hygiene is bad.
Something we did partly for the sake of avoiding arguments of "That's my drink you just finished" was we had plastic cups (ie unbreakable) for each child, in a colour we chose for each one. easy child was red, difficult child 1 was blue (first girl, first boy). easy child 2/difficult child 2 was yellow (because it went well with her red hair and was the only remaining primary colour) and then when difficult child 3 arrived, we'd run out of primary colours so we hunted around and decided on green. it quickly became second nature and we found the fringe benefit of it was, we didn't catch the usual bugs off each other. From what we've worked out, the biggest cause of cross-infection in the family is kids sharing cups with parents. We use the dishwasher efficiently, it sterilises things moderately well. But instead of getting a glass out of the cupboard, each kid would get THEIR cup from the sink and simply refill it. It saved a lot on wash-up; one cup did all day and then got hand-washed that night or thrown in the dishwasher at the end of the day. Or not - sometimes we didn't get around to it. But it didn't matter, because nobody else used that cup.
The chopping board rule - we don't have the multicoloured ones but have our own system. We slice bread and chop vegetables, fruit etc on a plastic chopping board. If I have to cut up raw meat, I will use our smaller plastic chopping board but it then goes straight into the dishwasher. We also do our utmost to avoid raw chicken especially, from coming into contact with the kitchen bench. I'll use the sink (stainless steel) to hold a bag of raw meat because once it's finished with and the sink empty, I can always rinse it with a splash from the kettle just after it's boiled.
Some people take big risks - I remember watching my sister defrost a chicken in a sink full of warm water. NOT a good idea, parts of it will warm up just enough to incubate bugs to big population densities. The water can also force these bugs into crevices in both the chook and anywhere else the water splashes, carrying lots of happy little salmonella bugs with it.
What I'm saying - there is a fine line between being safe and sensible, and being obsessive and unhealthy. Understanding why is a big start.
I've been re-reading the James Herriot "All Creatures Great and Small" books about a vet in Yorkshire. in some of them he describes the "knacker man" whose job involved carting off the dead animals (or ones destined to be slaughtered). Backc at the man's yard he would butcher the healthy meat but most of what went to him was too far gone for huiman consumption, so it would get boiled down to make pig meal, the bones ground for fertiliser etc. Nothing got wasted. A lot of these dead animals had died of disease or were loaded with germs and/or parasites, but the knacker man's little kids played happily in the piles of decaying dead animals and the author noted that these were the healthiest kids in town. Scientists are now explaining why this is so, but that was not known at the time the books were written.
I grew up in a backyard farm. I played with a range of animals and also did chores around them as well. We put their manure on the garden and ate the produce. We also were very healthy. We didn't use antibacterials, although we did use a lot of boiling water to clean up the milking things and anything we used with raw meat (especially chicken).
Duckie is enough of a scientist to understand current knowledge of the immune system. Her concern about her own allergies could be triggering some early Obsessive Compulsive Disorder (OCD) issues. Knowledge may be the way around this for her. It could also be a control issue - if she can keep the nastiest allergens out of her environment, she feels safer.
It only becomes a problem when it begins to interfere with your life.
Marg
Then she told us, in front of M, that if he got to the point where his hands got dry and cracked, we should really be worried. 
