People should focus on a long-term and balanced diet instead of "extreme self-medication" when detoxing after the festive period, according to a leading dietician.
Aisling Snedker, a clinical dietician based in Galway, said: "People need to remember that just because herbal medicines are natural, does not mean they are safe."
Ms Snedker's warning comes following the hospitalisation of a woman in England who suffered sever hyponatraemia.
The woman had consumed excess fluids and various herbal remedies whilst attempting a New Year "detox".
Hyponatremia is a condition that occurs when the level of sodium in the blood is abnormally low.
It can cause severe nausea, seizures and headaches, as well as a severe fatigue.
The 47-year-old English woman who was hospitalised had been consuming more fluids and herbal medicines than usual, including valerian root, over the New Year period.
She was admitted to hospital following a brief period of confusion and repetitive behaviour, such as teeth grinding which lasted for an hour.
She then collapsed and suffered a seizure.
The woman had also been taking herbal remedies for various minor symptoms and was regularly consuming milk thistle, molkosan, l-theanine, glutamine, vitamin B compound, vervain, sage tea, green tea and valerian root.
The difference in "hydration and fluid intoxication can narrow in some individuals", said Ms Snedker.
"If your electrolytes are out of range already, this will be exacerbated by excessive hydration.
"If people want to turn over a new leaf, they should take the long-term route as opposed to extreme self-medication," she said.
Ms Snedker said: "People need to remember that herbs are plants and have active properties and they need to consider the same precautions if taking medication."
However, Ms Snedker said: "I am not against herbal medicine in balance but self-medicating, like anything, can lead to unwanted situations."
The woman's case was studied by doctors from Milton Keynes Hospital NHS Foundation Trust for the British Medical Journal, who said "despite marketing suggesting otherwise, all-natural products are not without side-effects".
"The complementary medicine market is very popular in the UK and the concept of the New Year 'detox' with all-natural products is appealing to those less concerned with evidence-based medicine and more with complementary medicine," the doctors said.
They noted that "excessive water intake as a way of 'purifying and cleansing' the body is also a popular regime with the belief that harmful waste products can thus be washed from the body".