Some individuals with pollen allergy experience mouth itching and swelling after eating certain *raw* fruits, vegetables and tree nuts. The condition is called [**oral allergy syndrome**][1] or **pollen-food syndrome.**

**A certain food allergy as such** may increase intestinal permeability **(leaky gut syndrome)** and allow additional allergens to enter the blood, which can result in multiple food allergies ([PubMed, 2016][2]).

"...perturbation of environmental factors **(infection, stress),** by increasing intestinal permeability and enhancing danger signals, may favour food allergy in susceptible individuals" ([PubMed, 2005][3]). 

As a side note, [food protein-induced enterocolitis syndrome (FPIES)][4] can develop in infants after introducing solid foods and can present with multiple food allergies. But:

> Unlike traditional IgE-mediated allergies, FPIES reactions do not
> manifest with itching, hives, swelling, coughing or wheezing, etc.

  [1]: https://acaai.org/allergies/types/food-allergies/types-food-allergy/oral-allergy-syndrome
  [2]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5288588/
  [3]: https://www.ncbi.nlm.nih.gov/pubmed/16292078/
  [4]: https://www.kidswithfoodallergies.org/page/food-protein-induced-enterocolitis-syndrome-fpies.aspx