Can you develop an immunity to chopping onions causing tears

onions

I just chopped a particularly strong onion, I noticed some slight irritation but no tears. I realized then that onions haven't made me cry for years, decades even. I use all kinds of onions and take no special precaution to prevent tears. I don't refrigerate them, remove the core, use goggles, light a candle, anything like that. Granted, I've gotten better (faster) at it over the years, but I remember hating chopping onions in my youth because of the eye irritation. It doesn't seem that speed alone could account for the difference in my reaction.

Can I chalk it up to a similar phenomenon that gives me asbestos fingers and my tolerance for extremely hot (spicy) food?

Best Answer

Given that the tear-causing effect of onions is due to a straight forward chemical process, it seems highly unlikely that you would develop any kind of actual immunity in terms of the effect. Scientific American describes it:

Peeling, cutting or crushing an onion's tissue releases enzymes called allinases, which convert these molecules to sulfenic acids. The sulfenic acids, in turn, spontaneously rearrange to form syn-propanethial-S-oxide, the chemical that triggers the tears. They also condense to form odorous thiosulfinates, coincidentally evoking the pungent odor associated with chopping onions and eliciting the false accusation that it is the odor that causes the weepy eye. Incidentally, sulfenic acid in garlic takes a different chemical route, sparing the eyes. The formation of syn-propanethial-S-oxide peaks at about 30 seconds after mechanical damage to the onion and completes its cycle of chemical evolution over about five minutes.

[ ... ] Free nerve endings [on the cornea] detect syn-propanethial-S-oxide on the cornea and drive activity in the ciliary nerve--which the central nervous system interprets as a burning sensation--in proportion to the compound's concentration. This nerve activity reflexively activates the autonomic fibers, which then carry a signal back to the eye ordering the lachrymal glands to wash the irritant away.

It turns out that newer science indicates the conversion is not spontaneous, but due to an enzyme for this purpose, now named lachrymatory-factor synthase.

What is likely, especially for an experienced cook are:

  • Improved knife skills and speed, lowering the amount of time in close contact with the irritating gasses produced by chopping onions
  • Increased tolerance for the specific sensation
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