Fish sourcing and allergy

4.3.1What fish allergy is

Fish allergy is an immune response to specific proteins in fish tissue. Parvalbumin is the principal one and it is heat stable, which is why cooking does not remove the allergen. Reactions range from mild to anaphylactic, and the severity of previous reactions is the best available guide to what a future one might look like, though it is not a reliable predictor. The NHS pages on allergies and on anaphylaxis are the correct starting points and they are written for patients rather than clinicians.

Two points are commonly confused in consultations. Fish allergy and shellfish allergy are different allergies to different proteins in different animals, and someone allergic to prawns is not thereby allergic to salmon. And allergy is not intolerance: a person who feels unwell after eating fish does not necessarily have an allergy, and someone who does have one should know it from proper assessment rather than from inference.

4.3.2What purification is designed to do

The extraction and purification process is aimed at isolating nucleic acid from everything else in the source tissue. Protein removal is central to it, both because protein is the allergen and because protein contamination in an injectable is an immunological risk in its own right. The process also targets endotoxin and microbial material, since the product is injected.

The result is a preparation in which residual protein is intended to be at a level too low to provoke a response. That is the manufacturer's specification and it is a reasonable one. What a patient cannot do is verify it, because batch level residual protein data is not published in a form available to the public.

4.3.3Why the absence of reports is weaker evidence than it sounds

A common line in consultations is that reactions have not been reported. This is probably accurate and it is a weaker reassurance than it appears, for a structural reason.

Private cosmetic practice in the United Kingdom has no mandatory adverse event reporting. The MHRA Yellow Card scheme covers medical devices and accepts reports from clinicians and from the public, but it is voluntary. There is no national register of procedures. A clinic experiencing an adverse event has no obligation to report it and has a commercial reason not to advertise it. In that environment, the absence of reports tells you considerably less than it would in a setting with mandatory reporting and a denominator.

None of this means reactions are occurring and being hidden. It means the reassurance rests on a surveillance system that would struggle to detect an uncommon event.

4.3.4How to raise it

Raise it at consultation, not in the treatment room. Be specific about what you are allergic to, how it was diagnosed, and what your worst reaction has been. Ask the practitioner what the manufacturer's instructions for use say about fish allergy, and ask for the answer from the document rather than from memory.

Ask for the conversation to be recorded in your notes. That is not a legal manoeuvre; it is how a clinical record is supposed to work, and it means that if you see a different clinician later, the information travels with you.

If you carry adrenaline auto injectors, bring them. If you have had anaphylaxis to anything, ask what emergency provision the clinic has and who is trained to use it. That question is a reasonable one to ask before any injectable procedure and it is answered well by good practices without any awkwardness.

4.3.5Beyond allergy: the other reasons sourcing matters

People decline animal derived products for reasons that are not medical, and a consent process that does not surface the origin of the material has failed on its own terms. Vegetarian and vegan patients, patients whose religious practice restricts animal products, and patients who simply prefer not to, all have a legitimate interest in being told before rather than after.

The right time to say so is the consultation, and the right question is simply what the product is made from. It should not require a patient to know in advance that the answer is fish.

4.3.6If it is not for you

We are not aware of an established plant derived or synthetic polynucleotide injectable in routine UK cosmetic use. If you are offered one, ask what the product is, who manufactures it, and whether it carries a UKCA or CE mark, and treat vagueness on those points as significant.

If a fish derived product is not acceptable to you, that is a complete answer and requires no further justification. Other categories of injectable exist that are not animal derived, hyaluronic acid produced by bacterial fermentation among them, and the article comparing regenerative injectables sets out what each one is and is not.