It shows an expert wearing pink gloves running her fingers through the 90-year-old woman's hair, exposing hundreds of the wriggling bugs caught in her roots.
The expert said it was "so bad" they had to send the woman to hospital.
"We had a 90-year-old woman come in and see us today and she had the worst case of lice we have ever seen," the expert said in the clip.
"It was so bad we had to send her to the ER."
Head lice are tiny wingless insects about the size of a sesame seed that live in the hair of humans and animals. They feed on blood by biting the skin.
The expert from The Lice Angels in the US shared a video of the woman which has been viewed more than 59 million times. Photo / TikTok / theliceangels
In a follow-up video the expert said they had sent the woman to hospital to get treated for her open wounds where she was given a course of antibiotic.
"We will then treat her in two weeks," the expert added.
While head lice do not spread disease, their bites can cause severe itching and sometimes skin irritation.
Usually, they are treated by a targeted conditioner spray to soak the hair before combing the critters out.
In Australia, head lice are one of the most commonly reported health complaints from parents and teachers.
According to NSW Health, a cheap conditioner can also do the trick in removing lice.
"Cover all of the (dry) hair with conditioner, detangle hair with normal comb and separate into sections," it states on the site.
"Then, using a fine long toothed metal lice comb, comb through the hair in sections. The conditioner does not kill lice but stuns them for about 20 minutes enabling easier removal. "The long toothed metal comb will remove nits and the stunned head lice."
It is then advised to wipe the comb on a white tissue and check for any lice or nits.
"Keep combing until no more appear on the tissue. This method should be done every second or third day until no nits and lice remain, usually about 7 to 10 days."
