Quick answer: A food allergy diary is a timed record of everything you eat and drink (including ingredients, brands and amounts), any reactions (what, when, how long, what you did), and possible cofactors such as exercise, alcohol or pain relievers. It helps your allergist take an accurate history and choose the right tests. It can't diagnose an allergy by itself. Any signs of anaphylaxis need epinephrine, if prescribed, and a 911 call.
If you've had hives after dinner or a scratchy throat after a snack and can't pin down why, a food allergy diary gives your allergist the details they need. Allergists rely heavily on your history, and NIH-sponsored guidelines say diagnosis needs a clear, specific history confirmed by testing [1].
This guide shows what to record, a sample entry, and the safety rules that matter more than any diary.
Key takeaways
- Anaphylaxis is an emergency. Use epinephrine if you have it and call 911. Don't wait to see if it passes [2][3].
- A diary supports diagnosis; it doesn't make one. Allergists confirm with targeted tests and, when needed, a supervised oral food challenge [1].
- Record ingredients, not just dish names. Save or photograph labels of packaged foods [2].
- Most food-allergy reactions start within minutes to hours of eating [1], but some, such as alpha-gal syndrome, typically start 2–6 hours later [4].
- Don't keep eating or "re-testing" a food you suspect caused a serious reaction [2], and skip IgG food panels [5].
What is a food allergy diary, and what can it do?
A food allergy diary is a record of what you eat and the symptoms that follow, kept so a clinician can look for repeated patterns. If, for example, every reaction follows a food containing milk, your allergist may focus testing on milk [2].
What a diary can do:
- Help narrow down which foods to test, so testing is targeted rather than a broad panel [1]
- Capture timing, amounts and cofactors you'd otherwise forget
- Show whether symptoms happen without the suspected food, which is also an important clue [1]
What it can't do:
- Confirm an allergy. Kids With Food Allergies notes a food diary "is not enough to diagnose a food allergy" [2]. Diagnosis requires a clear history confirmed by testing, with an oral food challenge as the reference standard when needed [1].
- Tell an allergy apart from a food intolerance on its own. Intolerances (such as lactose intolerance) usually cause digestive symptoms without the immune reaction of an allergy. That distinction matters for safety, and only your clinician can make it.
What should you record in a food allergy diary?
Record every food and drink with the time, amount and ingredients, and every symptom with its timing, duration and treatment. Allergy guidance stresses including everything, not just the main part of a meal: condiments, drinks, supplements and medicines too [2].
| Field | What to write | Why it matters |
|---|---|---|
| Time eaten | Exact time | Links reactions to exposures |
| Food & amount | "1 slice", "half a cup", "3 bites" | Some reactions depend on dose |
| Ingredients | Full list for mixed dishes; photo of packaged-food labels [2] | Hidden allergens hide in sauces, seasonings and coatings |
| Brand / restaurant | Name; note cross-contact risk (shared fryer, bakery) | Explains reactions to "safe" foods |
| Raw vs cooked | "Raw apple" vs "baked apple" | Cooking can change how some foods affect you |
| Symptom(s) | Hives, swelling, itchy mouth, vomiting, cramps, wheeze, cough, dizziness… | Pattern of organs involved |
| Onset & duration | "Started 15 min after; lasted 2 h" | Typical allergy timing vs delayed reactions |
| Cofactors | Exercise, alcohol, NSAIDs/aspirin, illness, sleep loss, period [1][2] | Can make reactions more likely or more severe |
| Treatment & response | Antihistamine, epinephrine, ER visit; what helped | Severity and need for an action plan |
| Photos | Rashes, swelling, labels [2] | Reactions often fade before your appointment |
How soon after eating do allergy symptoms start?
Most food-allergic reactions start within minutes to a few hours of eating. NIH-sponsored guidelines say to consider food allergy when typical symptoms occur "within minutes to hours" of eating a food, especially if they follow the same food more than once [1]. Typical symptoms include hives, swelling, wheezing, mouth itch, cough, nausea, vomiting and anaphylaxis [1].
Some reactions are delayed:
- Alpha-gal syndrome, a red-meat allergy linked to tick bites, commonly causes symptoms 2–6 hours after eating mammalian meat or other products containing alpha-gal [4]. CDC estimates as many as 450,000 people in the US may have been affected [4]. Delayed reactions are easy to miss without a diary that records dinner and the 2 a.m. hives.
- Second-wave reactions: after anaphylaxis, a second reaction (a biphasic reaction) can occur as long as 12–24 hours after the first [3]. Record it if it happens.
That's why your diary should record the time of every meal and snack, not just the one you suspect.
What does a good allergy diary entry look like?
A good entry lets your allergist reconstruct the event without asking you to remember. Compare:
Vague: "Had a reaction after lunch, took Benadryl."
Useful (illustrative example, not a real patient):
| Time | Entry |
|---|---|
| 12:10 | Lunch at [restaurant]: chicken satay (4 skewers) with peanut-style sauce, jasmine rice, iced tea. Asked about nuts; told the sauce was "nut-free". Photo of menu saved. |
| 12:25 | Itchy mouth and lips, then hives on neck and chest. |
| 12:35 | Throat feels tight, hoarse voice. |
| 12:37 | Used epinephrine auto-injector; called 911. |
| 13:30 | ER: treated and observed for several hours. Discharged 17:45. |
| Cofactors | Ran 5 km at 07:00; no alcohol; no NSAIDs; slept 6 h. |
| Follow-up | Restaurant later confirmed the sauce contained cashew. |
And for suspected milder or delayed reactions:
| Day | Time eaten | Food (ingredients, amount) | Symptom & onset | Duration | Cofactors | Treatment |
|---|---|---|---|---|---|---|
| Tue | 19:00 | Beef burger (beef patty, bun, cheddar, ketchup), 1 | Hives on arms at 23:30 (4.5 h later), cramps | 3 h | 1 beer | Antihistamine |
| Thu | 12:30 | Turkey sandwich (turkey, wheat bread, mayo) | None | — | — | — |
| Sat | 18:45 | Pork ribs, coleslaw | Hives + diarrhea at 22:10 (3.5 h later) | 4 h | Walked 30 min after | Antihistamine |
A delayed pattern after mammalian meat, like this one, is the kind of history worth showing an allergist. It doesn't prove alpha-gal syndrome; only testing and clinical assessment can say.
What should you bring to the allergist?
Bring the diary itself, a short summary of each reaction, photos, and a list of medicines. The NIH-sponsored guidelines describe history questions allergists ask, including whether factors such as exercise, alcohol, aspirin or NSAIDs were involved, and how long symptoms lasted [1].
Checklist:
- Diary covering the period of your reactions (at least a couple of weeks with entries before and after each reaction is helpful)
- One-line summary per reaction: food, amount, time to symptoms, symptoms, treatment, outcome
- Photos of rashes or swelling, and of ingredient labels [2]
- ER or urgent care discharge papers
- All medicines and supplements, including antihistamines (ask whether to stop any before skin testing)
- Foods you eat regularly without problems, which helps rule things out
- Questions: "Which tests do I need?", "Do I need an epinephrine prescription and an action plan?", "Is an oral food challenge appropriate for me?"
Avoid ordering IgG food panels as a shortcut. The American Academy of Allergy, Asthma & Immunology (AAAAI) recommends against IgG testing to diagnose food allergies or intolerances [5], and the guideline summary says such tests "should be discouraged" [1]. For more on testing vs tracking, see food intolerance tests vs a food diary.
For general tips on handing over records, see how to share your logs with your doctor.
How to keep a food allergy diary day to day
Log at the time. Write entries as you eat and as symptoms start. Reaction details fade within hours. Our guide to keeping a symptom diary your doctor will use explains why recall is unreliable.
Make it easy:
- Photograph meals and every ingredient label [2].
- Use the same symptom words each time.
- Note "no symptoms" days too.
- Keep logging for a while after a reaction, so there's a record of what you ate safely.
If you use an app, inspect the actual record you plan to share and ask your practice which format it accepts. The Get Regular App tour and Doctor Report explanation describe the intended workflow; check current availability and the file itself before relying on it for a visit.
Safety rule: don't deliberately re-eat a food to "check" whether it caused a reaction. If you know or suspect which food caused anaphylaxis, don't eat it again until your allergist has assessed you [2]. Oral food challenges should only be done by trained professionals with emergency treatment immediately available [1].
When to get emergency help
Anaphylaxis can start suddenly and worsen quickly. Early signs can be mild, such as a runny nose, a rash or a "strange feeling", and then progress fast [3]. Use epinephrine if you have it and call 911 if you have symptoms such as [3]:
- Trouble breathing, wheezing, or a tight throat
- Hoarse voice, or swelling of the lips, tongue or face
- Hives or swelling
- Repeated vomiting, abdominal pain or diarrhea after a suspected allergen
- Dizziness or fainting
Severity is unpredictable. Even people who've only had mild reactions in the past can have anaphylaxis [3]. Go to the emergency room after using epinephrine, and be aware that a second reaction can occur 12–24 hours later [3].
See an allergist (or ask your doctor for a referral) if you've had any reaction you suspect was caused by food, even a mild one. And see a doctor about ongoing digestive symptoms after eating, such as bloating, diarrhea or pain. Those may have other causes worth checking, including intolerances, celiac disease or IBS.
FAQ
How long should I keep a food allergy diary? There's no fixed length. Keep it long enough to capture a few reactions or suspected reactions, plus the days before and after. A couple of weeks is a common minimum, but your allergist may ask for more. Keep logging if reactions are infrequent.
Can a food diary diagnose a food allergy? No. It helps your allergist decide which foods to test, but diagnosis requires a clear history confirmed by testing, and sometimes a supervised oral food challenge [1][2].
What's the difference between a food allergy diary and a food intolerance diary? The format is similar, but an allergy diary puts more weight on rapid-onset symptoms (hives, swelling, breathing problems), exact ingredients, cofactors and emergency treatment. An intolerance diary focuses more on digestive symptoms over hours to days and on portion sizes.
Is there a food journal app for allergies? Several apps can log foods and symptoms. Choose one that records exact times, ingredients and free-text notes, and can export or share a summary with your allergist. Whatever you use, keep your emergency action plan separate and accessible. An app is not a substitute for it.
Sources
- American Family Physician (AAFP). Summary of the NIAID-Sponsored Food Allergy Guidelines. Am Fam Physician 2012;86(1):43. https://www.aafp.org/pubs/afp/issues/2012/0701/p43.html
- Kids With Food Allergies (AAFA). Using a Food Diary to Sort Out Food Allergies. https://kidswithfoodallergies.org/living-with-food-allergies/new-food-allergy-diagnosis/diagnose-food-allergy-food-diary/
- American College of Allergy, Asthma and Immunology. Anaphylaxis. https://acaai.org/allergies/symptoms/anaphylaxis/
- CDC. Emerging Tick Bite-Associated Meat Allergy Potentially Affects Thousands (27 Jul 2023). https://www.cdc.gov/media/releases/2023/p0727-emerging-tick-bites.html
- AAAAI. The myth of IgG food panel testing. https://www.aaaai.org/tools-for-the-public/conditions-library/allergies/igg-food-test
This article is for general education and isn't medical advice. Get Regular is a tracking app — it doesn't diagnose or treat any condition. If you have red-flag symptoms or ongoing changes in your digestion, talk to a doctor.