The moment Susannah from Trinny and Susannah was "humiliated" by her hairdresser.

Whether it’s a bad cut or a problem with the colouring, most of us have had one or two less-than-ideal moments at the hairdresser’s.

But TV presenter and style expert Susannah Constantine’s trip to the salon three years ago takes the prize for most mortifying.

Writing for the Daily Mail, the What Not to Wear host told of how she was left “humiliated” when a hair stylist told her he couldn’t colour her hair because she had head lice.

Susannah explained that as she flicked through a magazine, her hairdresser was combing her hair and she gasped before saying she "needed a minute".

"Assuming it was a momentary technicality over bleach, I resumed my contemplation of the latest fashions that I could neither fit into nor afford," the mum-of-three wrote.

Before long the chief colourist came over, clearly embarrassed, to tell her: "Susannah, I’m really sorry but we can’t continue colouring... You have nits."

"Seeing the shock and revulsion on my face, he instead tried a little soothing. 'Don’t worry,' he continued, 'we see it all the time'."

Listen: See? Everyone gets lice at some point. (Post continues.)

For Susannah, who worked with friend Trinny Woodhall on a style column and various TV shows and specials, that day was the beginning of a traumatic three-year ordeal to get rid of a "full-blown infestation" of super-nits.

As the 55-year-old explained, the lice she had caught were resistant to normal treatments, and so, as a last resort, she recently when to a special clinic in Britain to undergo an extreme treatment.

"My hair is to be pig-tailed, scorched and, in a coup de théâtre, professionally ‘hoovered’ in an attempt to rid me once and for all of the lice."

At the dedicated clinic, she had the lice and eggs - which she thinks she caught from a helmet at a go-kart track - sucked from her head. Her scalp was then blasted with hot air to dehydrate any remaining eggs.

After the 90-minute treatment, which cost almost $350 (£200), Susannah said she was feeling "confident" the little suckers had all been eradicated and were hopefully gone for good.

She said she was sharing her story in the hopes it encouraged other parents to "fess-up" to a widespread problem that needs discussing.

"...Unknowing adults are a big part of the problem, and this is why I am ‘outing’ myself."

"No doubt I will be ostracised by some and ridiculed by others, but someone has to put their nit-infested head on the block and it might as well be me."