Fault
Chlorophenol
A medicinal, sticking-plaster note formed when chlorine meets phenols — almost always a cleaning or water-treatment failure.
Also called band-aid, plaster, TCP, medicinal, plastic.
What it tastes and smells like
Responsible compound: chlorophenols.
Chlorine or chloramine in brewing water, or residual sanitiser on equipment, reacts with naturally occurring phenols from malt to form chlorophenols. The threshold is among the lowest of any beer compound, so contamination levels far below anything noticeable in water are enough to ruin a batch.
This is the single most common fault in homebrewing that traces to tap water, and it is entirely preventable.
Where it may be expected
Phenolic character is correct in these styles, but the *kind* of phenol differs. Clove, pepper and smoke are yeast- or malt-derived and belong. Sticking plaster, antiseptic and TCP are chlorophenols and are a fault in every style without exception.
Intensity and context decide. In the styles below a restrained version of this can be part of the character; the same character running past that is still a fault there.
Styles this tends to affect
Not where it belongs — where it is most likely to appear when something has gone wrong.
- Grodziskie — A low-strength Polish wheat beer brewed entirely from oak-smoked malt: light, sharply hopped, very fizzy and unmistakably smoky.
- Lichtenhainer — A historical Thuringian smoked wheat beer that is also lightly sour — an unusual combination of smoke and lactic acidity.
- Rauchbier — A Märzen-based lager brewed with beechwood-smoked malt — intensely smoky, often compared to bacon, over a clean malt base.
If you are drinking it
A sticking-plaster or antiseptic note is always a fault, in any style. It is harmless but genuinely unpleasant, and worth returning.
Not a safety issue. Beer’s alcohol, hop compounds and low pH make it inhospitable to organisms that cause illness.
What causes it
| Cause | Stage | How often | Who can act |
|---|---|---|---|
| Brewing with untreated municipal water containing chlorine or chloramine. Chloramine is more persistent than chlorine and does not simply boil off. | raw materials | most common | brewer |
| Chlorine-based sanitiser left on equipment or in bottles and not adequately rinsed. | packaging | common | brewer |
| Wild yeast contamination producing phenolic compounds directly, which can read as medicinal in a style not meant to have them. | fermentation | occasional | brewer |
If you are brewing it
- Brewer: Treat brewing water with a campden tablet, which removes both chlorine and chloramine, or use carbon-filtered water. Boiling alone does not remove chloramine. (prevents)
- Brewer: Switch to a no-rinse acid sanitiser, or rinse chlorine-based sanitiser thoroughly with treated water. (prevents)
Where in the process this comes from
Steps that can produce this fault when they go wrong. Each links to what the step is for and how it is controlled.
- Water treatment — Adjust the mineral content and alkalinity of brewing water so the mash reaches a workable pH and the finished beer has the intended balance.
Often confused with
- Infection — unexpected sourness, barnyard
Evidence
What BeerHQ knows about this, and how. Every statement carries the state of the evidence behind it rather than being presented flatly as fact.
The medicinal, TCP or plastic character of chlorophenols forms when chlorine or chloramine in brewing water reacts with phenolic compounds from malt and hops, and is preventable by treating the water before use.
Backed by a source
Sources: Water: A Comprehensive Guide for Brewers — print; Brewing: Science and Practice — print