Ask an AI assistant about allergy medicine and it will usually tell you the generic is the same thing for less. In mapou's September study, ChatGPT, Gemini, Claude and Grok steered shoppers to the generic in 85% to 100% of one-off answers.
But a shopper rarely asks one question. So mapou ran 20 full shopping conversations, 5 with each assistant. Each simulated shopper kept asking until they decided to buy something or to see a doctor.
15 of the 20 conversations ended in a purchase. 8 of those were the generic or a store brand. 6 were a brand, and 1 was both.
The numbers
| Assistant | Bought | Generic or store brand | Brand, or brand and generic | Sent to a doctor | Steered to generic, one-off answers |
|---|---|---|---|---|---|
| ChatGPT | 4 | 3 | 1 | 1 | 85% |
| Gemini | 3 | 0 | 3 | 2 | 100% |
| Claude | 4 | 1 | 3 | 1 | 85% |
| Grok | 4 | 4 | 0 | 1 | 100% |
20 conversations, 37 assistant turns, September 2026. Steering is from one-off answers to 55 allergy questions.
Grok's shoppers bought the generic every time, 4 of 4. Gemini's never bought the generic alone: 2 bought a brand and 1 bought both. Claude's mostly bought brands too, 3 of 4.
So the assistant that steers hardest in a single answer isn't always the one that moves the purchase. Gemini steered to the generic in 100% of one-off answers, tied with Grok for the most. Over a full conversation, its shoppers still left with a brand.
Store brands came up by name. 3 purchases were a store brand, like Kirkland at Costco. Costco was also the 8th most-named name across all the one-off answers, brands included, in 14% of them.
Some shoppers were sent to a doctor. 5 conversations ended there, three of them for the 67-year-old on blood-pressure medication, who is told to avoid decongestants.
| Shopper | ChatGPT | Gemini | Claude | Grok |
|---|---|---|---|---|
| 67, on blood-pressure medication | See a doctor | See a doctor | See a doctor | Generic |
| 38, severe hay fever | Generic | Brand | Brand | Generic |
| 27, new cat, new allergy | Brand | Brand and generic | Brand | Generic |
| 34, daily user, price shopper | Store brand | See a doctor | Store brand | See a doctor |
| 41, buying for a six-year-old | Generic | Brand | Brand | Store brand |
Final decision of each conversation.
What it means
mapou's read: the generic pitch is simple and true, so AI repeats it in almost every single answer. But in a real conversation the shopper adds details, like a stuffy nose that needs a spray, a child's dose or a preference for one form, and the recommendation often lands on a named product. Which product depends heavily on the assistant.
What this doesn't show
This is a small sample, 15 purchases, so treat the differences between assistants as directional. The shoppers are simulated. It shows what AI recommends, not whether the advice is medically right.
How we measured this
- Conversations
- 20 synthetic shopper conversations, September 2026: 5 allergy personas (for example a 67-year-old on blood-pressure medication and a parent buying for a six-year-old), each run once against ChatGPT, Gemini, Claude and Grok. The shopper keeps asking until it decides to buy or to see a doctor.
- What was counted
- Each conversation's final decision, hand-classified as generic (the ingredient name), store brand (for example Kirkland), brand (for example Flonase), both, or see a doctor.
- Single answers
- 55 allergy questions asked once of each engine. Steering to the generic was detected with fixed phrase patterns (same active ingredient, bioequivalent and so on).
- Engines
- ChatGPT (gpt-5.4-mini), Gemini, Claude and Grok through one shared search layer with web search on.
- Limits
- Small samples: 15 purchases, 3 to 4 per assistant. This measures what AI recommends, not whether the advice is medically right.
Cite this article
mapou, “AI tells allergy shoppers the generic is the same. After a full conversation, 6 in 15 still bought a brand.,” mapou.ai, October 4, 2026. https://mapou.ai/articles/ai-sends-allergy-shoppers-to-costco
Reporters can reach mapou through for more on the method, other breakdowns or a comment.
Does AI send your shoppers to the generic?
mapou runs full shopping conversations in your category every month and shows how often each AI assistant moves shoppers from your brand to a generic or a store brand.
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