A new study found that of 14 products examined, two contained sucrose (table sugar), six contained alcohol and six contain lidocaine, an anaesthetic used to numb tissue.
Researcher Nigel Monaghan, from Public Health Wales, publishing in the British Dental Journal, said there is little evidence that the products are actually effective in reducing teething pain.
The British Dental Association (BDA) backed his view, urging parents to be alert to the ingredients in teething products.
The study comes after the Medicines and Healthcare products Regulatory Agency (MHRA) announced in December that teething products with lidocaine would no longer be sold in supermarkets and high street shops, and would only be found in pharmacies.
The medicines regulator conducted a review that found products with lidocaine were linked with a “very small” risk of harm and there was little evidence they work.
Instead, it said parents should massage the gums or use a teething ring.
The latest study looked at 14 products, including Anbesol, Dentinox, Calgel, Bonjela Junior and Boots own brand.
It concluded: “Despite a lack of evidence of effectiveness for teething products, of the 14 licensed products in the UK, nine contain one or more of sucrose, alcohol or lidocaine.
“There is an opportunity to develop new guidance to steer health professionals and the public away from these potentially harmful products.”
The BDA said the products containing sugar increased the risk of tooth decay.
Meanwhile, exposure to alcohol may lead to poor sleep, while lidocaine was a risk in high doses.
BDA chairman Mick Armstrong said: “Parents buying teething powders to save infants from distress won’t always realise they’re offering their kids sugars, alcohol or lidocaine.
“Buying a licensed product should offer confidence you’re making a safe choice.
“The reality is consumers are navigating a minefield of potentially harmful ingredients.
“We need to see real change in the way these products are licensed and marketed, and clear guidance so parents understand the risks.
“If your little one is suffering then a teething ring kept cool in the fridge is all you need.”
A spokesman for the MHRA said none of the products it licenses contain sucrose.
Furthermore, alcohol had a function to prevent products spoiling and was at very low levels, he said.
“It may also enhance the solubility of the active ingredients or facilitating the penetration of active substances into the gums,” he said.
He added: “To help babies and children with teething, parents and caregivers should try non-medicine options such as rubbing or massaging the gums or a teething ring.
“If you suspect that your child has experienced a side effect to a medicine, please report this to us through our Yellow Card Scheme.”
A spokesman for Boots said the product in the research was discontinued in January.