Just a quick question; I was looking up the MSDS for o-Toluic Acid for an experiment when I came across this in the "Hazards Identification" section.

Very hazardous in case of skin contact (irritant), ....
Slightly hazardous in case of skin contact (permeator).

How should this warning be interpreted?

  • 7
    $\begingroup$ I'd interpret it as "wear gloves" ;) $\endgroup$
    – canadianer
    Sep 17, 2014 at 21:52
  • 1
    $\begingroup$ @canadianer As a computational chemist myself, I interpret it as "deadly". $\endgroup$ Sep 19, 2014 at 13:26

2 Answers 2


An irritant is a chemical, which is not corrosive, but which causes a reversible inflammatory effect on living tissue by chemical action at the site of contact. There are specific lab tests to determine the ranking of an irritant, but something which is rated as very hazardous is likely to cause a very severe reaction upon exposure.

A permeator is a chemical which can pass through the outer protective dermal layers and into the body, and can either expose the body to toxic effects of that chemical OR act as a carrier for other toxic/hazardous chemicals.

Other common classes of hazardous chemicals include corrosive and sensitizer.

o-Toluic acid is a strong irritant, but moderate permeator. Depending on your level of experience in handling chemicals, simply getting the advice to 'wear gloves' may leave you a little underprepared. You should take this to mean that you should not allow any skin contact; full length sleeves (lab coat), eye protection and THE CORRECT TYPE of gloves. Using the incorrect type of gloves is worse than using no gloves at all, as it gives you a false sense of security. Select the correct type of gloves using a suitable selection tool or guide, such as this one from Ansell.

As a strong irritant, you should also avoid breathing any vapours or fumes, so it means handling this chemical in a suitably ventilated area.

AS with any risk assessment, it also means that before you handle the chemical you have an understanding of the response procedures in the event of things going wrong. That is, from your MSDS, you need to know Section 4:First Aid Measures prior to any procedure you undertake. It is no good having to find and read the MSDS after you have splashed yourself with this stuff.

  • $\begingroup$ Thanks! I just wasn't sure because of the contradictory wording between the two lines $\endgroup$
    – qwersjc
    Sep 19, 2014 at 2:50

As canadianer said, wear gloves.

Irritant means just as it sounds, it will irritate your skin (ie: itching, rashes, strange sensations, ect.)

Permeator means that it can pass through the skin.


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