Warning: Warnings ahead! Interpreting common product warning labels

Life is full of warnings and, clearly, some are more helpful than others. But warning labels are so common that you may begin to ignore them. Or, you may not notice them at all. Just how should one respond to all the red exclamation points, bold print, and highlighted advice that you see on food labels, prescriptions, billboards, and elsewhere? Many of these do not provide the reason they are there or tell you what may happen if you ignore them. It’s enough to confuse even the most reasonable person who just wants to do the right thing.

Warning labels deal with risk. Some are there solely to inform you that something bad may happen. Others offer you a warning so you can reduce your risk: “There are peanuts in this product” means, “if that’s a problem for you, this would be a good time to choose something else!”

Some tell you something you probably already know (“The cigarettes you are about to smoke may cause serious health problems”) or something that is primarily there to legally protect the manufacturer in case something bad happens in the future (“The artificial sweetener you are about to use has been found to cause cancer in laboratory animals,” meaning “We don’t actually know if it will harm you but if it does, you can’t say you weren’t warned!”)

When you see your doctor, you may get a prescription that comes with a wealth of warnings and recommendations to reduce risk. As is the case for food labels, the reasons vary and the consequences of ignoring these warnings vary as well.

Among the medically important and common food label warnings I found in my kitchen are:

• Aspartame — This sweetener, found in NutraSweet and many similar products, contains an amino acid (one of the building blocks of protein) called phenylalanine. For people with a rare, inherited condition called phenylketonuria (PKU), phenylalanine builds up in the body and causes serious problems, including brain damage. Newborns are routinely screened for this condition and if detected, they must restrict their dietary intake of phenylalanine. That’s why sweeteners containing aspartame carry a warning: Phenylketonurics: contains phenylalanine. Most experts agree that as long as you don’t have PKU or take in massive amounts of aspartame, the sweetener seems to be harmless.
• Peanuts — Serious allergic reaction to peanuts is among the most common of all food allergies, so foods that may contain even minor amounts of peanuts have warning labels to let you know. Unfortunately, those labels may be hard to interpret: How concerned should potential consumers be when encountering "may contain traces of peanuts" or "made in the same factory as foods containing peanuts"? Or, the labels may simply be wrong: A recent Canadian study found that certain chocolate contained far more peanuts than the “possible trace amounts” listed on the label. In the absence of reliably accurate and standardized warnings, people with a significant peanut allergy should avoid all foods with even a trace of peanuts.  
• Eggs — Salmonella enteritidis is a bacterium that can be ingested from raw or undercooked eggs. That’s why the warning label on eggs urges you to cook them thoroughly, to wash your hands well after cracking raw eggs, and to wash cooking surfaces if they have come into contact with raw eggs.

Your doctor or pharmacist may warn you about a prescription you are about to fill. In addition to the long list of potential side effects, pharmacies typically have rolls of stickers to apply to pill bottles with suggestions or warnings about how to take the medicine. Among the most common are:

• Take after food — This recommendation is common for many medicines because eating food buffers the acid in the stomach, and that can make medicines such as ibuprofen or aspirin easier to take.
• Take on an empty stomach — Some medicines will not be absorbed properly unless taken on an empty stomach; the common medicines for osteoporosis, alendronate (Fosamax) and risedronate (Actonel), are examples. In addition, a warning label for these medicines will urge you to take them with a full glass of water and to remain upright — that is, don’t go back to bed if you take it in the morning — to ensure it goes down properly all the way into the stomach; if it does not, it may cause serious irritation and damage to the esophagus called erosive esophagitis.
• Beware of interactions — Because mixing medications (including over-the-counter medicines) can lead to a variety of problems, warning labels often mention not to take certain medicines if you are already taking another one. Common examples of how problems occur include:
• • Additive dose — Avoid taking Motrin and Advil together. Because these are identical medications, taking both just increases the dose higher than intended; stomach upset, a bleeding ulcer, or kidney failure could follow.
  • Additive effect — Avoid alcohol with sedatives. Some medicines are mildly sedating and are well tolerated on their own, especially if taken before bed; but alcoholic beverages are also sedating, and the combination is sometimes much more than you bargained for.
  • Counteracting drugs — Avoid taking birth control pills with phenytoin. The effectiveness of the first medication is reduced due to the addition of the second medicine; this may not mean the second medicine has to be avoided, but the dosage of the first medication may need to be changed or, in the case of birth control pills, another contraceptive method may be necessary.
• Avoid the sun — Certain medications are called “photosensitizers” because they increase one’s sensitivity to the effects of the sun. Examples include tetracycline and sulfa antibiotics (such as Bactrim). Sun exposure while taking these medicines may induce rash, fever, and a general feeling of sickness after only a short time outside.
• Allergic reactions — While being allergic to a particular drug is a clear enough reason to avoid it, some warning labels are not intuitive. For example, the warning that accompanies the flu shot states that you should avoid the vaccination if you are allergic to eggs. That’s because the vaccine is prepared from chicken eggs and people with serious allergic reactions to eggs may have a bad reaction to the flu shot. Similarly, a person who is allergic to aspirin should not take Advil or Aleve or other nonsteroidal anti-inflammatory drugs (NSAIDs). It’s not that they contain aspirin, but because they are chemically similar, a bad reaction to one is more likely if you have a bad reaction to any of the others.

With so much risk and so many warnings, what’s a person to do? It’s worth asking whether we may be exposed to too many warnings about risks that are quite small. In fact, there is a risk of providing too many warnings, including the possibility that warnings will be ignored or overlooked. There’s also the risk of not taking a medication due to fears about taking it incorrectly. I know patients with arthritis who skip their medications because they are not having a meal. They lose the benefit of the medicine because they were trying to follow the warning label’s recommendation — in fact, most of the time, a single dose on an empty stomach is not likely to cause problems.

Do your best to read about your medications and follow instructions. If they contradict each other (which does sometimes occur), call your doctor or pharmacist to sort it out. Also, ask your doctor or pharmacist how seriously you should take a warning on a particular medication. Like I tell my patients with arthritis worried about occasionally taking their medication on an empty stomach — it’s okay to ignore the warning every now and then. Of course, there are other times when ignoring a warning could be harmful, so be sure to talk to a clinician about your particular situation. 

Risk is a part of the human condition — there is risk associated with eating, breathing, and crossing the street. And although we may worry most about the risk of developing disease, we should also consider the risks of its treatment. Of course, for any given condition there may also be risks associated with not getting treatment. You can reduce your risks related to the medicines by asking questions, and by learning more about what your doctor and pharmacist (and their little stickers) are saying. When you understand why a warning is there in the first place, it’s a lot easier to decide whether it should concern you.

Have you found warnings on medicines or foods helpful? Have you seen any that confused you? How would you change food or drug labeling about risks?

Robert H. Shmerling, M.D. is an Associate Physician at Beth Israel Deaconess Medical Center. He is also a Senior Medical Editor for Harvard Health Publications.

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This content is not intended to substitute for personalized medical advice, diagnosis, or treatment from your healthcare provider. Read our full disclaimer.

This content is not intended to substitute for personalized medical advice, diagnosis, or treatment from your healthcare provider. Read our full disclaimer.