Garlic and onion are two of the highest-FODMAP foods most of us eat — and they hide in stock, gravy and seasoning blends, so you can react without realising. Our £49 hair screen covers 700+ items and gives you a shortlist worth exploring first, so one focused elimination diet replaces months of guessing. Report within 3 days of your sample reaching our UK lab.

What this screen is — and what it is not

What it is

• A food-response screen: the Gold panel gives you a shortlist of foods — including garlic, onion and other common high-FODMAP items — that you may want to explore through a structured elimination diet
• A wide net: we screen your sample across 700+ items, which can help you decide where to focus when you start mapping your personal triggers
• Non-invasive and fast: just 9 or 10 strands of hair, with results within 3 days of your sample reaching our UK lab, and no fasting or prep needed
• A starting point, not an endpoint: the screen suggests which foods to remove and reintroduce systematically, so you can work out for yourself what affects you
• Backed by our 90-day money-back guarantee — follow your 6-week elimination plan, keep a food diary, and if your symptoms haven’t improved we’ll refund you in full

What it is not

• A measure of FODMAP content in foods: it doesn’t tell you how much FODMAP any food contains
• A diagnosis of IBS, food intolerance or anything else: only a qualified clinician can do that, and we don’t claim to — we simply help you explore foods through diet
• A test of your gut, enzymes or absorption: we don’t measure how well you absorb carbohydrates or break down fructans
• A validated diagnostic method: hair-based screening points you toward foods to trial; it does not prove how your body handles garlic and onion. The proof comes from your own elimination and diary
• A cure, treatment or fix: any change in how you feel comes from the elimination-diet process you follow, not from the screen — the screen only points you toward foods to try removing

How garlic and onion can lead to bloating through FODMAPs

Garlic and onion are among the highest-FODMAP everyday foods most of us eat. FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols — a group of carbohydrates that the small intestine absorbs poorly. In garlic and onion the main one is fructans, a type of oligosaccharide that passes largely undigested into the colon. There, gut bacteria ferment the fructans and produce gas, which for some people brings on bloating, cramping and looser stools, often within one to three hours of eating.

NOT AN ALLERGY: This is general nutrition science about the foods, not something our screen can confirm is happening inside you. It is also not an allergy — the immune system isn’t involved. It is better thought of as a digestive-load issue: the small intestine simply can’t absorb these particular carbohydrates well, so they reach the colon intact and bacteria do the rest.

DOSE MATTERS: How much discomfort follows depends on portion size — for sensitive people even a single clove of garlic or a quarter of an onion can be enough — and on everything else eaten that day, since a meal stacked with several FODMAP foods adds up.

WORTH KNOWING: Cooking does not reduce fructan content. Fructans are stable when heated, so a well-cooked onion carries just as much FODMAP as a raw one. That is partly why garlic and onion catch people out — they hide in stocks, gravies, seasoning blends and the catch-all ‘natural flavouring’ on processed foods, so you can be eating them without realising.

WHERE THE SCREEN FITS: The only reliable way to learn whether they affect you personally is a structured elimination and reintroduction diet, ideally with input from your GP or a registered dietitian. A food screen can give you a sensible shortlist to start from, but the answers come from the diet, not the test reading.

Does this sound like you?

• Bloating within 30–90 minutes of garlic- or onion-flavoured meals, even in small amounts
• Visible distension after soups, curries, stir-fries or sauces
• Cramping, gas or loose stools one to three hours after flavoured dishes
• Bloating after shop-bought or restaurant meals with ‘natural flavouring’ or seasoning blends
• Bloating that eases when you avoid garlic and onion for 5–7 days, then returns when you eat them again
• More comfortable cooking from scratch without garlic or onion than eating processed foods

Related foods worth checking at the same time

• Other high-fructan vegetables: shallots, leeks, artichokes and asparagus contain similar fructans, so if garlic and onion bother you these are worth watching too
• Wheat and other grains: wheat, rye and barley also contain fructans, and people who notice garlic and onion often find these add to their overall FODMAP load
• High-FODMAP fruits: apples, pears and dried fruits like dates and figs are high in fructose, and eating one alongside garlic or onion can stack the load in a single sitting
• Legumes and beans: chickpeas, lentils and other beans contain galacto-oligosaccharides (GOS), a different FODMAP that often turns up alongside fructan sensitivity
• Processed foods with hidden garlic and onion: seasoning blends, gravy mixes, stock cubes, ready meals, dressings, canned soups and sauces frequently include garlic or onion powder — sometimes only as ‘natural flavouring’ — so several meals a day could be quietly adding up
• Dehydrated versions: garlic powder, onion powder and instant minced garlic are concentrated, so a teaspoon of powder carries far more fructan than a single fresh clove

Examples of what the 700+ item panel covers

• Garlic (fresh clove)
• Garlic powder
• Onion (white, yellow, red varieties)
• Onion powder
• Shallots
• Leeks (white and green parts)
• Spring onion (scallion) bulb (high FODMAP)
• Spring onion (scallion) green tops (low FODMAP)
• Chives (low FODMAP garnish alternative)
• Garlic-infused oil (low FODMAP)
• Seasoning blends with garlic and onion
• Stock cubes (often contain garlic and onion)
• Gravy powders (commonly garlic and onion-based)
• Ready-meal sauces (hidden garlic and onion in ‘natural flavouring’)
• Worcestershire sauce (contains garlic and onion)

How to run a focused elimination

Plan for A 6-week core elimination (all garlic and onion out), then careful structured reintroduction — where possible with guidance from your GP or a registered dietitian.

1. Weeks 1–2: Remove all garlic and onion in every form — fresh, cooked, powdered and hidden in processed foods. Read labels closely for seasoning blends, stocks, gravies, sauces, dressings and ready meals. Cook from scratch using fresh herbs (rosemary, thyme, basil), spices (cumin, paprika, black pepper) and garlic-infused oils with the solids fully removed. Start your food and symptom diary on day one.
2. Weeks 3–4: By now, many people whose discomfort was driven by garlic and onion notice things settling. Jot down your energy, digestion and how you feel each day. If nothing has changed, other FODMAP foods (wheat, beans, high-FODMAP fruit) may be worth exploring alongside or instead — a good moment to check back in with your GP or dietitian.
3. Weeks 5–6: Hold the course to the end of the core plan, even if you already feel better. A settled baseline — and a diary kept across all six weeks — is what makes your reintroduction readable, and it’s also what the 90-day guarantee asks for.
4. After week 6: Start reintroduction. Bring back garlic or onion one at a time, spacing each trial by 4–5 days. Begin with the lowest-FODMAP forms: garlic-infused oil (whole cloves removed, leaving only the flavour) or the green tops of spring onions. Eat a small test portion (about ½ teaspoon of infused oil, or a small handful of green spring onion tops) and watch for 48 hours.
5. Next: If the infused oil or spring onion tops sat well, gently increase the portion at your next trial (after another 4–5 day gap). If you stay comfortable, those forms are likely fine for you. Then try a little raw onion (a 1–2 cm cube with a meal), then cooked onion (perhaps a quarter of a small onion in soup), again spacing trials by 4–5 days. Finally test garlic: start with a single fresh clove in a cooked dish.
6. Ongoing: Map your own tolerance and turn it into a kitchen routine. You might find garlic-infused oil and spring onion tops are fine but fresh garlic or whole onions aren’t. Write these boundaries down — they become your personal FODMAP map. Reach for infused oil, use spring onion greens as a garnish, lean on fresh herbs for flavour, and keep checking labels on stocks, sauces and seasoning blends for hidden garlic and onion powder.

Reintroduce garlic and onion in their lowest-FODMAP forms first (garlic-infused oil, green spring onion tops), then move on to whole fresh or cooked versions only once you’ve confirmed you’re comfortable at the lower forms. Leave 4–5 days between each new trial so any symptoms have time to settle. If discomfort returns after a trial, set that form aside for at least a week, then try it once more to confirm before deciding to leave it out for good. Remember that FODMAP responses are dose-dependent — you might be fine with a tiny amount of garlic in a large meal but not a whole clove on its own. Mapping your personal threshold can take a few more weeks after the core plan, and that’s normal — the 90-day guarantee asks you to follow your plan for at least 6 weeks with a food diary, so start your diary on day one. A registered dietitian can help you do this without cutting out more than you need to.

One customer’s experience

Fatima, 32, often felt bloated within 30 minutes of cooked meals and assumed her digestion was just slowing down. While meal-planning she spotted a pattern: every flavoured dish — curries, stir-fries, soups, even shop-bought pasta sauces — seemed to leave her puffy. She saw her GP first, who looked into her symptoms before she made any big dietary changes. Curious about FODMAPs, the fermentable carbohydrates found in foods like garlic and onion, Fatima used her IntoleranceLab report as a shortlist of foods to trial. She then ran a focused 6-week elimination — removing garlic and onion completely, with a food diary from day one — and during the structured reintroduction that followed she found that garlic-infused oil (with the bulb removed) and the green tops of spring onions sat fine with her. Her mum’s soup, remade with homemade stock instead of a garlic-onion paste, felt more comfortable too. She now reads ingredient lists, watches for hidden garlic and onion powder in seasoning blends, and cooks with infused oils and fresh herbs. To be clear, it was the elimination process — not the screen itself — that showed her what her body was reacting to. Fatima’s pattern is one illustration; your own diary is what maps yours.

Common questions

What’s the difference between a FODMAP response and a food allergy to garlic or onion?

They’re very different. A true allergy to garlic or onion is an immune reaction that can cause immediate symptoms such as hives, throat swelling or, rarely, anaphylaxis — if you ever have symptoms like these, seek urgent medical help. A FODMAP response is not an immune reaction at all: the small intestine struggles to absorb fructans, which then ferment in the colon and can produce gas and bloating. It typically comes on more slowly (one to three hours later) and depends on the dose. Our screen does not test for allergy and is not a way to diagnose either one — it simply gives you a shortlist of foods you might choose to trial through an elimination diet. Any allergy concerns should always go to your GP.

Why does garlic-infused oil seem fine even if fresh garlic doesn’t suit me?

It comes down to chemistry. FODMAP fructans are carbohydrates and don’t dissolve in oil. When you infuse oil with whole garlic cloves and then take the solids out, you keep the flavour compounds (which are oil-soluble) without the fructans (which stay in the removed solids). It’s important the cloves are fully removed — if you leave them in, fructans can leach into the oil over time. Properly made and strained, garlic-infused oil is genuinely low in FODMAP, which is why many people find it more comfortable than fresh garlic.

Are the green tops of spring onions really low FODMAP?

Yes. The white and pale-green parts of spring onions (scallions) are high in fructans, but the dark green tops are low FODMAP. That’s because the bulb and white base store fructans as an energy reserve while the leafy green part doesn’t. You can use the green tops freely as a garnish or flavouring; if you’re keeping FODMAPs low, set the white bulb aside.

How do I spot hidden garlic and onion in processed foods?

Look out for: seasoning blends (sometimes tucked inside ‘spice mix’ or ‘herb blend’); stock cubes (garlic and onion are standard); gravy mixes (almost always include the powders); ready-meal sauces and dressings (where ‘natural flavouring’ can mean concentrated garlic and onion); Worcestershire sauce (contains both); and canned soups. When you’re not sure, contact the manufacturer or choose fresh ingredients you control yourself.

Why doesn’t cooking garlic or onion stop the bloating if they affect me?

Cooking changes the texture and taste but not the fructan content. Fructans are stable carbohydrates that survive heating, so a slow-cooked onion soup carries just as much FODMAP as raw onion. If garlic or onion don’t suit you, cooking won’t change that — the options are to leave them out or switch to lower-FODMAP alternatives like garlic-infused oil or spring onion greens.

Could both garlic/onion and wheat be affecting me?

It’s possible. Both wheat and garlic/onion contain fructans, so people who notice one sometimes notice both. If you remove them together you take out a chunk of your overall FODMAP load at once, which can make a clear difference. The catch is you won’t know which mattered — so during reintroduction, test them separately (4–5 days apart) to see whether it’s one, the other or both. Some people manage a little wheat but not garlic, or the reverse.

If garlic-infused oil and spring onion tops suit me, do I still need to avoid whole garlic and onion?

It depends on your own threshold. Some people handle small amounts of whole garlic or onion — a single clove, a thin slice in a large meal — without trouble; others don’t. Your reintroduction trials are how you find that out. Many people build their cooking around the low-FODMAP alternatives (infused oil, spring onion greens, fresh herbs) and keep whole garlic or onion for occasional small amounts, or leave them out. A dietitian can help you keep your diet as varied as possible.

How soon after changing my diet might I feel different?

Many people notice their bloating easing within a few days to a week of removing garlic and onion, though it varies — some feel a difference within a day, others take a couple of weeks. Keep a food and symptom diary through your elimination phase so you can see the pattern for yourself. Any improvement comes from the elimination process you follow, not from the screen; the screen only suggests which foods to try removing first.

Should I see my GP before trying a FODMAP elimination diet?

Yes — it’s a sensible first step, especially with persistent bloating, cramping or changes in your bowel habits. Your GP can look into other possible causes before you start cutting foods out. If they think a FODMAP approach is reasonable, they may refer you to a registered dietitian, who can guide you through elimination and reintroduction safely so you don’t restrict your diet more than necessary. Our screen is there to help you explore, but your GP’s assessment comes first.

Related reading

• Explore bloating and digestive symptoms
• Understand wheat and FODMAP fructans
• Learn about dairy and lactose
• Explore fructose & high-FODMAP sugars