4-Methylhippuric Acid (4MHA)

Optimal Result: 0 - 74 mcg/g.

MHAs are metabolites of xylene (dimethylbenzenes). Xylenes are widely used as solvents in products including paints, detergents, pesticides, fuel, perfumes, and exhaust fumes. The main effect of inhaling xylene vapor is depression of the central nervous system (CNS), with symptoms such as headache, dizziness, nausea, and vomiting.

Long-term exposure may lead to irritability, depression, insomnia, agitation, extreme tiredness, tremors, hearing loss, impaired concentration, and short-term memory loss. A condition called chronic solvent-induced encephalopathy, commonly known as "organic solvent syndrome" has been associated with xylene exposure.

What does it mean if your 4-Methylhippuric Acid (4MHA) result is too high?

Avoid/reduce exposure to these substances.

Xylenes (dimethylbenzenes) are found not only in common products such as paints, lacquers, pesticides, cleaning fluids, fuel and exhaust fumes, but also in perfumes and insect repellents. Xylenes are oxidized in the liver and bound to glycine before eliminated in urine. High exposures to xylene create an increase in oxidative stress, causing symptoms such as nausea, vomiting, dizziness, central nervous system depression, and death. Occupational exposure is often found in pathology laboratories where xylene is used for tissue processing.


Methylhippuric acid (2,-3,4-MHA) is the result of exposure to the solvent xylene that is widespread in the environment. Xylene is found in paints, lacquers, cleaning agents, pesticides, and gasoline. It is also used in the pathology laboratory for tissue processing.

High exposure to xylene may cause nausea, vomiting, dizziness, incoordination, central nervous system depression, and even death. An exposure to 100 ppm xylene in the air resulted in a urine value of 3140 µg/g creatinine for methylhippuric acid.

Rats given xylene experienced a significant decrease in locomotor activity, deficits in learning ability and memory loss. These xylene -induced behavioral changes were associated with a decrease in beta-endorphins.

Possible treatment options:

Treatment begins with removing all potential sources of exposure. Elimination of xylene can be accelerated by sauna treatment, the Hubbard detoxification protocol employing niacin supplementation, supplementation with glycine to encourage metabolism of xylene to methylhippuric acid in the liver, or by glutathione (reduced) supplementation (oral, intravenous, transdermal, or precursors such as N-acetyl cysteine [NAC]).

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