⚠️ Safety Verdict: Caution - Allergic Reactions Possible
E131 (Patent Blue V) is approved for food use but can cause allergic reactions in sensitive individuals. It's more commonly known for medical use where serious allergic reactions have been documented. Not one of the "Southampton Six" but still a synthetic dye worth noting.
⚠️ Allergy Warning
E131 has been associated with allergic reactions including:
- Skin reactions (urticaria, itching)
- Breathing difficulties (rare but documented)
- Anaphylaxis (very rare, mainly with medical injection)
If you have allergies to other dyes or aspirin sensitivity, be cautious.
What is E131 (Patent Blue V)?
E131 is Patent Blue V, a synthetic triphenylmethane dye that creates a blue-violet colour.
Key facts:
- Also known as: Food Blue 5, CI 42051
- Synthetic dye – made from petroleum derivatives
- Blue-violet colour
- Widely used in medicine for lymph node mapping
Where is E131 Found?
Food Products:
- Scotch eggs (coating colouring)
- Blue confectionery
- Beverages
- Some desserts
Medical Uses:
- Sentinel lymph node biopsy – to trace lymph nodes in cancer surgery
- Diagnostic procedures
💡 More Common in Medicine
E131 is actually more widely used in medical procedures than in food. When injected for surgery, allergic reactions are more serious – this is where most allergy reports come from. In food, the amounts are much smaller and reactions are rarer.
Health Concerns
1. Allergic Reactions
- Documented allergic reactions in sensitive individuals
- Cross-reactivity possible with other blue dyes
- Aspirin-sensitive people may be more at risk
2. Synthetic Dye Concerns
- Petroleum-derived – not a natural colour
- Not in the "Southampton Six" – but still synthetic
- Some parents prefer to avoid all synthetic dyes
Regulatory Status
UK/EU: Approved with ADI of 5mg per kg body weight
US: NOT approved for food use – this is important if comparing products
Note: Banned in US food but allowed in UK/EU
Who Should Avoid E131?
🚫 Consider Avoiding:
- People with dye allergies
- Those with aspirin sensitivity
- Anyone who's had reactions to blue dyes before
- Parents following precautionary approach with children
The Bottom Line
- ⚠️ Allergic reactions possible – documented cases
- ⚠️ Synthetic dye – petroleum-derived
- ✅ Approved in UK/EU (but not US)
- ✅ Not in "Southampton Six" hyperactivity colours
- 💡 More common in medicine than food
Our recommendation: E131 is approved but has more documented allergy concerns than some other colours. If you're allergy-prone or prefer to avoid synthetic dyes, check labels carefully.
Last updated: February 2026