UKH

What do we reckon? Chemical, biological or physical contamination? 
 

Thanks in advance.

Allergens are proteins or glycoproteins. Which foods? What allergens?

Any food product containing any of the 14 defined allergens. 
 

In food safety, physical contamination would be something like a piece of metal from a piece of machinery, biological would be pathogenic bacteria or pre-formed toxins from that bacteria and chemical would be something like cleaning chemicals. Where would allergens fit into that would you think? 

Metals can induce allergy, although usually through skin contact, but they are small in molecular weight and need to interact with a protein or larger chemical to cause allergy. These substances are called haptens. 

Toxins from microorganisms may be allergenic eg yeasts on the skin cause marked hypersensitivity in dogs but often cause harm by a different (non-hypersensitivity mechanisms).

The examples you give are not commonly thought of as major allergens. I am not familiar with the 14 defined allergens - do you have a link. 

https://www.food.gov.uk/sites/default/files/media/document/top-allergy-type...

If you're doing the online food hygiene certificate you need to pass without help from UKC

If you're not, then the answer is they class as 4th type of contamination. Biological is actual microbial and is bacteria or fungal. Chemical is chemicals in their own right not byproduct of microbial.

Shellfish is great. You can get physical from a bit of shell, microbial from things they carry, allergic due to the proteins, and chemical from build up of mercury.