What is this growing in my cellar?

[SameToo]

It’s a bit damp and where the paint is coming off, this is growing. Is it fungal spores? Is it likely to be harmful?

Looks like minerals leaching through due to damp getting in.

Is exactly what I was about to say Queen!

Thank you @ShrikeAttack and @QueenStromba. Is it harmful?

No.

Lovely. Thank you so much!

Yes it's the salt from the bricks. Happens on cold weather on newly put up walls etc. It's completely harmless and you can just brush it off.