• Girls with high chemical exposure have lower levels of a certain thyroid hormone

• The thyroid ensures brain development, with hormones ‘setting the schedule’

• For unknown reasons, the impact was seen to a lesser extent in boys than girls 

• Chemicals are linked to asthma, and lower IQ and development in children

• Parents should avoid chemical-laden shampoos, nail varnishes and vinyl floors 

By Alexandra Thompson Health Reporter For Mailonline

PUBLISHED: 10:37 EDT, 31 May 2017 | UPDATED: 10:37 EDT, 31 May 2017

Exposure to chemicals found in shampoos and toys during early childhood may seriously damage the mental development of youngsters, new research suggests.

Girls with high concentrations of certain chemicals, known as phthalates, in their blood have lower levels of a thyroid hormone, a study found.

Study author Pam Factor-Litvak of Columbia University, said: ‘The thyroid acts as the master controller of brain development.

‘Thyroid hormones set the schedule, and if the timing is out of synch, there may be later consequences in the brain.’

Previous research suggests up to 70 percent of the products we apply to our skin gets absorbed into our bloodstream, with our scalps having one of the highest absorption rates of anywhere on our bodies.

Phthalates are thought to mimic hormones, particularly estrogen, leading to hormonal-disruption driven disorders.