Oxalic Acid Is Already in Your Honey: What the Residue Numbers Actually Say

Oxalic Acid Is Already in Your Honey: What the Residue Numbers Actually Say

The residue objection is the most reasonable thing anyone says against oxalic acid. You are putting an acid into a box that produces food. Wanting to know what ends up in the jar is not paranoia, it is diligence.

It is also a question with an actual answer, measured repeatedly, and the answer is not the one most people expect.

---

Honey is an acidic food, and always has been

Honey typically sits around pH 3.9. It is more acidic than tomato juice. That acidity comes from a suite of organic acids the bees and the nectar put there — gluconic acid dominates, produced by glucose oxidase, and alongside it sit citric, malic, succinic, formic, lactic and oxalic acids in smaller amounts.

Oxalic acid is not a contaminant in that list. It is a constituent. The USDA Agricultural Research Service describes it as “ubiquitous in the environment, found naturally in many plants and vegetables, as well as in honey.” Nectar carries it in from the plants, and plants make a great deal of it.

The measurement that settles it

Bogdanov and colleagues at the Swiss bee research station did the work properly. They measured 33 samples of honey from untreated colonies and found oxalic acid ranging from 11 to 119 mg/kg.

Note the spread. The highest untreated honey in that set carried ten times the oxalic acid of the lowest untreated honey. That is ordinary variation between floral sources, seasons and locations, with no beekeeper involved at all.

Then they treated colonies under field conditions and measured again. Their finding: the oxalic acid content remained unchanged, even after two successive treatments during the same autumn.

Whatever the treatment contributed was smaller than the difference between one untreated honey and another. You cannot detect it against the background, because the background is larger than the signal.

Put it next to the rest of your diet

Food values from the USDA database for oxalic acid content of selected vegetables; honey from Bogdanov et al. 2002. Comparisons use the midpoint of the honey range. Produce oxalate varies widely with variety and growing conditions.

A single 100 g serving of spinach delivers more oxalic acid than several kilograms of honey. If oxalic acid in honey were a meaningful dietary concern, the salad would have been the problem long before the beehive was.

What the EPA concluded

When the EPA granted a tolerance exemption for oxalic acid in honey in 2021, it did so on the basis that the quantity arriving from labelled use “is not expected to exceed levels that naturally occur in various products in consumer diets.” The agency’s framing was that oxalic acid residues in honey from labelled use “would not be substantially different to other naturally occurring products.”

A tolerance exemption is not a shrug. It is a determination that the exposure does not warrant a numerical limit.

The wax question, which matters more than people realise

Honey is the thing people ask about. Wax is where residues actually accumulate, and it is where the different treatments genuinely separate.

Oxalic acid is water-soluble. Wax is not. Water-soluble compounds do not partition into wax and build up there across seasons. Fat-soluble compounds do, and they stay for years, moving into new foundation when old comb is rendered.

Worth sitting with: thymol is the plant-derived, natural-sounding one, and it is the one that shows up in wax and can change how your honey tastes. Origin did not predict the outcome. Solubility did. We go further into that in is oxalic acid natural or synthetic.

Does it change the honey itself?

Separately from residue, there is the question of whether treatment alters honey’s composition or quality — sugars, enzymes, HMF, the things a lab measures. A 2026 University of Belgrade study followed ten colonies for 17 weeks and tested 183 honey and 187 beeswax samples, and found neither oxalic acid nor thymol shifted the composition of either. We cover that study, and its caveats, in does oxalic acid affect honey quality.

None of this overrides your label

Here is where we get boring on purpose.

The science on residue is reassuring. The label is still the law. If your product’s label restricts use with honey supers in place, that restriction applies regardless of what any study measured, and “but Bogdanov said” is not a defence. Read the label on the container in your hand, because labels differ between products and get amended over time. We go through the practical side in treating bees during the honey flow.

What would actually create a residue problem

• Massively overdosing. Two grams per deep brood box is the working dose. Studies measuring no residue change were measuring labelled rates, not someone emptying the jar into the pan.
• Dribbling into supers. A syringe of oxalic acid solution run over frames is a different exposure from vapor condensing as dry crystals. The dribble method is not intended for honey supers.
• Treating a colony that is actively storing nectar in supers you will harvest. Not because of a measured risk, but because it is the case the label is written to prevent.
• Using an unregistered product. Wood bleach from the hardware store has no label, no purity guarantee and no legal standing. Which oxalic acid to use for bees.

Used as labelled, the residue question is answered. It was answered in 2002, and nothing measured since has overturned it.

Related reading

• What is oxalic acid? A plain-English guide
• Is oxalic acid natural or synthetic?
• Treating bees during the honey flow
• Which oxalic acid should you use to treat bees?

Sources

• Bogdanov, S., Charrière, J.-D., Imdorf, A., Kilchenmann, V. & Fluri, P., “Determination of residues in honey after treatments with formic and oxalic acid under field conditions”, Apidologie 33(4):399–409, 2002
• USDA Agricultural Research Service, Bee Research Laboratory, Oxalic Acid FAQs
• United States Department of Agriculture, USDA database for oxalic acid content of selected vegetables, 1984
• EZ-OX Tablets label, EPA Reg. No. 101743-2, accepted 27 January 2026, US EPA

Happy Beekeeping from the Lorob Bees Team

General beekeeping information, not a substitute for the product label. Always read and follow the label of any product you use in a hive.