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Health, Science, Symptoms

Allergy Symptoms Checker – Dizziness, light-headedness or fainting


Dizziness or light-headedness is usually caused by a decrease in blood flow to the brain.  This occurs in response to the slowing of the heart rate or a drop in blood pressure (hypotension).  In extreme cases, this can lead to a sudden loss of consciousness, or fainting (syncope) [1]. Hypotension and slowing of the heart rate as part of an allergic reaction to food are mediated by a chemical called histamine.  Histamine has many effects on the body and is released by your immune system in response to a food allergen. It causes blood vessels to dilate or widen, thus resulting in a sudden and potentially severe drop in blood pressure [2].


Do Not Ignore This Symptoms

If you experience a feeling of dizziness or light-headedness after eating certain foods, you need to identify exactly what your triggers are, as this is classed as a moderate to severe reaction, and can often herald the onset of anaphylaxis.  Anaphylaxis is the most severe allergic reaction, and can quickly become life-threatening. Immediate medical support should always be sought if the risk of anaphylaxis is high.

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Track Your Triggers

If your symptoms are not severe but are still causing you discomfort and anxiety, a symptom and trigger tracking app like AlliApp can be extremely helpful.  Often, when you have an allergy or intolerance to a food, your reactions worsen every time they occur.  Therefore, it is extremely important that you identify your triggers. Keeping a record of what you are eating and any symptoms such as dizziness that occur even a few hours later is the most efficient way to do this.  Some people can also experience blurred vision or confusion together with light-headedness, which also indicates a potentially severe allergic reaction to food.

Another important reason for using a symptom tracking app is that other underlying conditions could be responsible for any dizziness or light-headedness experienced.  If food allergies or intolerances are not responsible for this, AlliApp can also help in eliminating foods as a cause of your symptoms, thus allowing you to explore other causes with your healthcare professionals.


Other articles of our series “The Six Main Symptoms of Food Allergy”:

Skin Irritation: Eczema and Hives

Wheezing And Other Breathing Difficulties

Abdominal Pain/Bloating/Diarrhoea/Constipation

Swelling Of Tongue/Face/Other Body Parts

Nausea and vomiting



  1. STARS (2018): Reflex Syncope (Neurally Mediated Syncope/Vasovagal Syncope)  Available online at: http://www.heartrhythmalliance.org/stars/uk/reflex-syncope-vasovagal-syncope [Accessed 29/09/18]
  2. Encyclopaedia Britannica (2018) ‘Histamine Biochemistry’ Available online at: https://www.britannica.com/science/histamine   [Accessed 01/10/18]

Dr Nicky, PhD, MBPsS - AlliApp Science

Nicky has a background in Radiography, Neuroscience and Psychology research. She is Mum to two girls, aged thirteen and eleven; both of whom have a combination of severe food allergies, food intolerances, asthma, eczema and hay fever. As such, she has spent her entire life as a parent finding ways to manage this, with a huge focus on food preparation, educating her daughters’ peers and their families about allergy awareness, and diet.

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