Spraying hydrogen peroxide and vinegar in sequence

Does it work?

Does not work

A state health department lists the combination among those not to be made. The claim's central assertion is its safety, and that is the part that fails. Whether the resulting peracetic acid disinfects is a separate question, unaddressed by that source, and it very likely does.

This is a verdict on whether the technique is effective. Whether it is safe on a particular surface is a separate question, answered below.

Where not to use it

Why it works

The claim's own reasoning is that keeping the two in separate bottles avoids mixing them, so each acts on the surface in turn with its own properties. That is not what happens: applying the second to a surface still wet with the first is combining them, with the surface as the vessel. Hydrogen peroxide and acetic acid react to form peracetic acid, a more aggressive oxidising agent than either. The technique's apparent effectiveness is therefore evidence that the reaction is occurring rather than evidence that the sequencing avoided it.

Background

The technique is presented as a sequence rather than a mixture — spray one, then the other, on the same surface — and that framing is exactly what makes it feel safe. Nothing is being combined in a bottle, both ingredients are household staples, and both have gentle reputations. It is nonetheless mixing two chemicals on a surface, and a state health department hazard alert lists it: hydrogen peroxide and vinegar together form peracetic acid, which can irritate the eyes, skin and lungs. Peracetic acid is used industrially as a disinfectant for the good reason that it is more aggressive than either starting material, which is also the reason the sequence appears to work better than either alone. This is a much less severe hazard than the chlorine and chloramine reactions, and the difference is worth stating plainly. What makes it worth knowing is that readers meet this one believing the opposite of what the evidence says.

What it does not do

• The hazard is irritation rather than the lung injury associated with chlorine and chloramine, which are a different order of harm
• It is frequently recommended for washing produce, where an irritant residue is the specific thing you do not want
• Neither ingredient alone is a substitute for a product formulated and tested for disinfection

What to use instead

• Detergent — A surfactant-based cleaner. The general-purpose answer for greasy and particulate soil, and the correct first choice far more often than any specialist product.
• Neutral cleaner — A near-neutral surfactant cleaner. The recommended answer for natural stone of every kind, and the least interesting product in the cupboard for good reasons.