Found loads of mould on clothes in wardrobe!

[Teppanyaki]

I keep old dresses in an Ikea wardrobe in my DC's bedroom along with DH's smart shirts etc as no room in my own wardrobe. Had a look today and loads of them have a few white mould spots on and two dresses are covered!
I've not worn them in years but we only moved here two years ago so they'd have been ok when I hung them up then.

The room is first floor and no signs of damp on the walls, in fact they were repainted since we moved in and nothing odd. It's one of the colder rooms in the house but is over the kitchen and heating on as normal as DC sleeps there. Any ideas why this is happening?

Ironically my 'normal' wardrobe is in the bathroom and we were a bit worried about damp in there on the clothes but they are all fine.

I get an allergic reaction when exposed to 'old' clothes (like clean, dry toddler clothes that have been stored in a storage bag for over a year)... is this just a visible manifestation of the same thing ?

One item was a leather skirt and luckily the spots wiped off easily but having tried to clean a mouldy buggy that was stored in the garage I'm not too hopeful about the bad ones (I'll never fit in them again anyway!). More curious about what's causing it - just the lack of wear/washing?

DC's clothes are in a separate cupboard and seem fine but they're worn regularly.

It sounds like you have too many clothes. Maybe you need to have a purge then give all the cupboards a good clean?

I have barely any clothes that fit me now, a handful of old work clothes that might one day be ok. There are about 10 of these dresses, some I was keeping for sentimental reasons. But yeah I should get rid. Not sure if the mould will come out of the two bad ones.
Will definitely clean the wardrobe! Just wondering where it originates?
If one item has it does it spread or does it form on all if it's damp or something (I'm still not convinced it's properly damp in there)?

Your reaction to old clothes is almost certainly to mould, yes.

What's causing it is being left for long enough in a damp enough environment. Dry clothes won't get mouldy. As to how... can't tell from here! That's for you to work out. Are the walls in that room cooler than you'd expect, did the paint take longer to dry than it said on the tin? Is the floor of the mouldy wardrobe damp at all?

Mould spreads by spores, but if any clothing you've not worn for a year makes you react then it's endemic in the house (unless they're always from this wardrobe). Have you checked under/behind the beds in the same room as the wardrobe? Peel back the carpet?

Thanks TheHighestSardine - it's a problem I've had in previous houses too, it could be a dust/dustmite allergy instead, although in this case these are clothes that are in sealed/zipped bags (never seen any mould etc on them).
There's no damp feeling or smells etc. I'll investigate the wardrobe further tomorrow but it seemed fine. In fact we keep nappies in the wardrobe which you might think would absorb any excess moisture?!

I mean the reaction to 'old' clothes is a problem I've always had. I've never had mouldy clothes before, only on things DH left in the garage as you might expect.