Officially Named Macadamia Allergens
| Macadamia allergen | Protein family | Molecular weight | What is known about cross-reactivity |
|---|---|---|---|
| Mac i 1 | Vicilin (7S globulin) | 50 kDa | Vicilins in other nuts and peanut are related, but clinical cross-reactivity with macadamia appears limited |
| Mac i 2 | Legumin (11S globulin) | 60 kDa | As above; macadamia allergy is often isolated |
Cross-Reactivity of Macadamia Nuts with Other Food Groups
Only two macadamia allergens are officially named: Mac i 1 (a vicilin) and Mac i 2 (a legumin). Related storage proteins occur in other nuts and in peanut, but published reports suggest macadamia allergy is often isolated and clinical cross-reactivity is limited. No macadamia 2S albumin or lipid transfer protein is officially named.
Risk Levels Based on Cross-Reactivity
| Food group | What is known | Practical advice |
|---|---|---|
| Other tree nuts | Co-allergy occurs; clinical cross-reactivity with macadamia appears limited | Each nut is assessed separately by an allergist |
| Peanut | Case reports of reactions; not an established cross-reactivity | Ask your allergist before eating macadamia if you are peanut-allergic |
| Rosaceae fruits (LTP) | No macadamia LTP is officially named | No established link |
Clinical Implications for Macadamia Allergy
- People with other tree-nut or peanut allergies should ask their allergist before eating macadamia; each nut is assessed separately.
- Macadamia can cause anaphylaxis on its own, even in people with no other nut allergy.
- Macadamia is on the FDA’s list of 12 tree nuts, so it is declared on US labels (as "macadamia nut" or "bush nut").
Anaphylaxis: act fast. After an exposure, any breathing symptom (wheeze, repeated cough, throat tightness, hoarse voice), fainting or dizziness, or symptoms in two or more body systems (for example hives plus vomiting) is anaphylaxis — even without hives.
- Give epinephrine right away (auto-injector or nasal spray). Do not wait to see if symptoms get better.
- Call 911, even if symptoms improve.
- Lie flat with legs raised (sit up if breathing is hard). Give a second dose after 5–15 minutes if there is no improvement.
Antihistamines and steroids do not treat anaphylaxis and must never delay epinephrine. Carry two doses and follow the written emergency action plan from your allergist.