I’m a hair expert — you’re making 2 major mistakes washing your locks

That’s cold.

Nicole Petty — deputy director at Milk + Blush, a hair extension retailer — is advising people to wash their hair in water 38 degrees Celsius or colder to seal the hair cuticle to increase shine and to lock in moisture to minimize dandruff.

“Whilst hot water can be beneficial for helping products absorb deep into the hair, it can also strip the hair of its natural oils, causing dryness and excessive oil production to compensate for a dehydrated scalp and tresses,” Petty explained to The Mirror in an interview published Saturday.

“This can cause scalp flaking and itchiness, resulting in strands feeling dry and brittle and leading to breakage. Instead, rinse your hair with lukewarm water to preserve the natural oils in your hair and retain moisture,” she added.

Petty also recommends not washing hair more than two or three times a week.

“The frequency of hair washing depends on your hair type and lifestyle, but over-washing is a common mistake that can damage your hair,” she revealed.

“Excessive washing can strip the natural oils and dry your locks out, leaving it prone to breakage and thinning, dulling the natural shine and increasing oil secretion to recoup lost moisture and stripping hair color faster,” she reasoned.

Petty noted that hair that quickly becomes oily may indicate over-washing or over-stripping.

“If this is the case, try training your hair by using dry shampoo to increase the longevity of time between washes, and avoid using overly stripping ingredients such as sulfates, parabens, and alcohol,” she instructed.

This week, The Post shared our list of the best shampoos for 2023, highlighting the top suds for those with dandruff; oily hair; thinning or fine hair; curly hair; and dry scalp.

“The key is to identify the primary challenge with the hair or scalp and specifically target that concern,”  Amy Abramite, hairstylist, salon educator and creative director at Maxine Ltd. in Chicago, told The Post. “For example, if the hair is feeling dry to the touch, a hydrating shampoo will nourish the strands and balance moisture for optimal health.”