Full mechanism, in text

More antioxidants isn't better

1 · Rhinovirus arrives

Most rhinoviruses lock onto ICAM-1 receptors on the lining of the nose and nasopharynx, get in and replicate there, so a cold starts in the nose and throat.Rhinovirus (RV) is the most common cause of the common cold. It enters through the nasal and oral mucosa, and most rhinoviruses target the ICAM-1 receptor (intercellular adhesion molecule 1), found on the epithelial cells of the nose and nasopharynx.

The icosahedral RV capsid is ringed with canyon structures, and the D1 domain of ICAM-1 fits into the canyon floor. Once locked on → the virus is taken in → its RNA enters the cytoplasm → it replicates → symptoms appear.

This is why a cold starts in the nose and throat — RV does not need the bloodstream; it multiplies right in the lining of the nose and nasopharynx.

2 · Lozenge · local Zn²⁺ release

Zinc lozenge design intent: dissolve slowly in the mouth so that Zn²⁺ goes into saliva and throat mucus and touches the infected lining directly.Key: what has to be released is free Zn²⁺, not a complex held by another ingredient.

Form:
· Zinc acetate or zinc gluconate lozenges, dissolved in the mouth, not swallowed
· Lozenges whose formula adds citric or tartaric acid: these ingredients grab zinc ions, so by the mechanism they should release less free zinc — this is the view of Hemilä, with no trial comparing them directly

Dose: 75-100 mg of elemental zinc a day, in portions (one lozenge every 2-3 hours, each about 13-23 mg); the three zinc acetate trials pooled by Hemilä used 80-92 mg/day. For ordinary throat sweets, read the label and count the daily total.

3 · Zn²⁺ may interfere locally

Local free Zn²⁺ may block the virus from binding ICAM-1 and damp local inflammation, both still hypotheses; trials show shorter colds, but the certainty is low.Local free Zn²⁺ may interfere with two things — both are still hypotheses, not directly shown in the human throat:

A. Blocking the virus from binding ICAM-1 — if the capsid cannot lock onto the receptor, the virus cannot get into the cell.

B. Damping local inflammation — much of the misery of a cold comes from the body's own inflammatory response.

So the idea is that a zinc lozenge works locally, not by boosting whole-body immunity. The actual effect: in the three zinc acetate lozenge with the right dose, timing and form (Hemilä 2016 individual-patient , N = 199), colds were about 2.7 days shorter than the 7-day average. Pooling the wider evidence, the current Cochrane review (Nault 2024) gives only low certainty: about 2.4 days shorter on average, with enormous variation between studies (I² = 97%).

4 · Three rules

Start zinc lozenges within 24 hours of symptoms, use them only for the days of the cold, and do not take them as a daily tonic.Rule 1 · Timing — start within 24 hours of symptom onset. That is what all three positive trials did; there is no evidence that starting later still helps.

Rule 2 · Use it only for the days of the cold — the adult tolerable upper intake level () for zinc is 40 mg/day, and going above it long term will:
· Block copper absorption — long term this can cause copper deficiency
· At the cold dose, the usual side effects are nausea and a bad taste in the mouth; in Nault 2024, non-serious side effects were indeed more common

Rule 3 · This is not a daily tonic — Nault 2024: zinc has little or no effect on preventing colds. Zinc lozenges are a short-term measure after a cold starts, not a wellness product.

Extra notes:
· Children: do not use adult doses; ask a doctor first
· Pregnancy: the zinc is 11 mg/day (age 19 and over); ask a doctor before short bursts of high doses
· Taking quinolone or tetracycline antibiotics: zinc binds them, so space the two apart; ask a pharmacist how far apart

Compared with vitamin C (Hemilä & Chalker 2013): taken regularly it does not reduce how often ordinary people catch colds and only shortens colds in adults by about 8%; started after a cold begins, it does not help.

So zinc lozenges (acetate or gluconate, started within 24 hours, 75-100 mg/day, for a few days only) have an effect that is real but limited, and the certainty of the evidence is not high.

Full mechanism, in text

1 · Rhinovirus arrives

2 · Lozenge · local Zn²⁺ release

3 · Zn²⁺ may interfere locally

4 · Three rules

Zinc lozenge vs rhinovirus

Full mechanism, in text

1 · Rhinovirus arrives

2 · Lozenge · local Zn²⁺ release

3 · Zn²⁺ may interfere locally

4 · Three rules

Zinc lozenge vs rhinovirus