Surprised man reading a leaflet for a medication while holding a pill

In the movie "Shrek 2," Antonio Banderas’s character, Puss in Boots, reads a list of side effects for a magic potion that include "… burning, itching, oozing, weeping …" While it’s one of the film’s funny moments aimed at adults, in real life, burning and itching are hardly the most unusual side effects a medication can have.

Before we delve into that, however, let’s settle once and for all exactly what is a side effect. According to the Food and Drug Administration or the FDA, side effects are "unwanted or unexpected events or reactions to a drug," which can be either an over-the-counter (OTC) medication or a prescription medicine. Now, there are many factors that can impact whether or not someone experiences a side effect, including if the person has allergies or is taking vitamins or another medication. And although some of the more usual side effects are tiredness and stomach discomfort, others can be so unusual that a person might not even realize that they are known side effects.

So, how can you recognize possible side effects from drugs? Well, a good place to start is understanding that a drug has the potential to affect any part of your body. For instance, even if you’re treating your eyes, the medication could affect your tongue, lungs, heart, and even your brain (via WebMD). This is why you shouldn’t ignore any changes that occur after you or someone you know starts taking a medication.

Your antidepressant can turn your urine blue or green

Close up of a sign for public restrooms for men and women on a painted wooden wall

Yes, you read that subhead correctly. While it’s logical that an oral medication could affect the shade of your urine, which usually ranges from light yellow to amber, there are several drugs that can make it blue or green (via Mayo Clinic). But that’s only the tip of the iceberg when it comes to one particular medication’s side effects. As WebMD explains, depression, anxiety, and other health issues that can affect a person mentally or emotionally are sometimes treated with amitriptyline. While this antidepressant helps to balance out the brain’s chemistry, it can also dramatically alter the color of urine to either blue or green. In addition, it can cause a host of other side effects like making it harder to urinate, constipation, blurry vision, dizzy spells, persistent dry mouth, and increases in weight.

While there are ways to manage some of these side effects (fiber for constipation and ice chips for dry mouth), there are more concerning ones that require medical attention, such as seizures, vomit that has the appearance of ground-up coffee beans, and losing consciousness. Regardless, if you are taking this medication, do not hesitate to talk to your healthcare professional if you experience any side effects. And don’t be embarrassed to tell them things like, "My urine is blue," or, "I pee green." This is important information that they can use to help you.

These eyedrops can weaken your sense of smell

Close-up of a woman using eyedrops

For someone with constantly irritated eyes, naphazoline can be a crucial item in their medicine cabinet. This eyedrop is used to treat itchiness, redness, and puffiness since it helps to decrease congestion in the eyes (via WebMD). And while some of its possible side effects like vision issues and eye discomfort are not surprising, naphazoline is also one of a few drugs that can weaken or alter your ability to smell (via WebMD and Mount Sinai). Plus, naphazoline eyedrops are sometimes combined with zinc sulfate, and zinc-based products may possibly also affect a person’s ability to pick up scents as well. Okay, but is that really such a big deal? After all, there are a number of odors you may wish were more muted. But remember, our senses of taste and smell are connected, so if you can’t take in a food’s aroma as well, it will not be as flavorful. This is why that usually tasty bowl of soup seems bland when you’re stuffed up with a cold.

Besides altering or diminishing your sense of smell, naphazoline can also cause fatigue, nausea, headaches, and perspiration (via WebMD). Ironically, another side effect of these eyedrops is they can actually make red, irritated eyes worse. If you experience of any of these side effects, contact your doctor.

A common cancer treatment can make your fingerprints disappear

Close-up of a thumb with a fingerprint imposed over it

In the movie "Men in Black," Will Smith’s character must have his fingerprints removed to join a secret organization that monitors extraterrestrial activity. The process involves a machine and (based on Smith’s reaction) appears to be painful. In real life, however, fingerprints can be chemically deleted by a drug used to treat breast and colorectal cancer (via Medscape Medical News). A study has found that the oral medication capecitabine can cause a person’s fingerprints to lose quality (via Medscape Medical News and JAMA Oncology). And as Dr. Ron Mathijssen, the senior author of the study, told Medscape Medical News, this can open the door to a number of identity-related issues. "… fingerprints are required to apply for a passport in the Netherlands, for entering certain countries including the U.S., and also they are increasingly being used to replace passwords to log into electronic devices such as laptops and smartphones."

While there is debate as to how capecitabine causes someone’s fingerprints to disappear, this side effect is not permanent. Once someone stops taking this medication, their fingerprints should come back in four weeks at the most. If you do take capecitabine, Dr. Mathijssen recommends getting a note from your doctor that explains why your fingerprints may be altered and keeping it on your person, especially if you’re planning to travel.

Your acid reflux medication may give you a "hairy tongue"

Close-up of a woman sticking out her tongue

Okay, take a deep breath. Even though this condition is officially called hairy tongue, it doesn’t literally mean hair grows out of someone’s tongue (via The American Academy of Oral Medication). Just like the skin on other areas of your body, the cells covering your tongue shed. But when something interferes with that natural shedding process, a coating forms on the tongue that looks similar to hair (via Healthline). And, yes, a type of medicine commonly used to treat acid reflux can cause this. According to Healthline, hairy tongue can be a side effect of proton pump inhibitors. Also called PPIs, these medications prevent your stomach from producing its usual amount of acid, as a key reason why someone experiences pain from reflux is stomach acid escaping into the esophagus and causing damage (via Healthline). However, if you’re taking PPIs, you’re more likely to one day look in the mirror and see what look like hair follicles on your tongue as the cells on the surface continue to grow and collect debris.

Although we understand that certain things can cause hairy tongue, we still haven’t completely connected the dots as to why they do (via Healthline). Other possible causes of hairy tongue include taking antibiotics, chewing tobacco, drinking too much coffee, smoking, radiation therapy, using cocaine, eating mainly soft foods, and not brushing your teeth properly.

A sleep medication can turn you into a sleepwalker

A woman sleepwalking

When most of us think of sleepwalking, the first image that pops into our minds is someone with their eyes closed and their arms outstretched in front of them. This setup can be a good source of comedy, especially when it’s combined with the myth that it’s dangerous to wake up a sleepwalker. However, in reality, sleepwalking is very different, and a medicine that can help you fall asleep can also make you more likely to experience it. As Healthline explains, sleepwalking (or somnambulism), is a rare side effect of zolpidem, a drug prescribed for sleep issues. Contrary to movies and TV shows, sleepwalkers don’t typically walk around as if in a trance. In fact, they may appear to be awake and going about their usual activities like eating, putting on clothes, or even just sitting up in bed. And as for their eyes, they usually alternate between being opened and closed, although they tend to appear glassy.

And though it can be related to medication, somnambulism in adults is more commonly a symptom of another medical condition like migraines or restless leg syndrome. However, if you are taking sleep medication and are walking in your sleep, it’s time to talk with your healthcare professional. And as for waking a sleepwalker, the National Sleep Foundation says it is safe to do as long as you don’t jolt them awake in the process (via Healthline).

Some drugs used for Parkinson’s disease can give you a gambling addiction

A roulette wheel covered with casino chips, dice, and cards on a roulette table

Sometimes side effects are obvious. If you get a rash every time you take a certain medication, then chances are you will connect the dots. But when someone is dealing with a particularly serious condition, it can be hard to separate the side effects from what could be the results of emotional stress.

Case in point, dopamine agonists are used to help patients with Parkinson’s disease (via Healthline). However, an analysis of a decade’s worth of information from the Food and Drug Administration (FDA) has found that these types of medications can cause dramatic changes in one’s behavior (via Healthline and JAMA Internal Medicine). Specifically, a person taking these drugs could lose some of their self-control and begin compulsively gambling, binge eating, excessively shopping, or become hypersexual. They also may cross over into criminal activity like stealing. And unlike some of the other medications on this list, this is not a rare side effect of dopamine agonists. In fact, the analysis indicates that one in seven people taking these drugs is affected psychologically. But while the number of people potentially dealing with these side effects is high, Dr. Howard Weiss, who published an accompanying commentary to the analysis, says, "I think we’re only seeing the tip of the iceberg. When doctors ask, ‘Are you having any side effects from the drugs?,’ nobody’s going to ask, ‘Are you going to casinos?’" (via Healthline).

This psoriasis treatment can lead to bumps around your nails

Close-up of four manicured fingernails

You’ve probably seen commercials advertising medications for the chronic skin disease called psoriasis. But did you know that there is more than one type of psoriasis? For example, while red scaly skin is a common feature of this condition, pustular psoriasis can lead to blisters forming throughout the body, according to the American Academy of Dermatology Association (AAD). Not a pleasant thought, but fortunately, the oral medication acitretin has been shown to help with several different types of psoriasis. Unfortunately, while it may reduce the blisters from pustular psoriasis, it also might lead to different types of bumps.

As AAD notes, one of acitretin’s side effects is patches of bumps popping up around the nails on both your fingers and toes. In addition, other potential side effects include chapped or peeling skin, skin that feels sticky, cracked lips, nails breaking more easily, discomfort in your joints and muscles, hair loss, and even not being able to see colors as vividly.

A common asthma medication can cause cataracts

Close-up of eye exam equipment

A person with asthma may have difficulty breathing because the tubes in their lungs get inflamed (via Medical News Today). So, it makes sense that asthmatics are sometimes prescribed corticosteroids, since these drugs can help decrease inflammation (via the Cleveland Clinic and Medical News Today). In fact, this type of drug is also used to treat conditions like rheumatoid arthritis and inflammatory bowel disease because of its anti-inflammatory properties. However, according to the Cleveland Clinic, a possible side effect of corticosteroids is they can lead to inflammation in your eyes — specifically in your retina. And even though the retina is located in the back of your eye, this type of swelling can cause cataracts to develop on the lenses in the front part of your eye (via Medical News Today). When this happens, your vision can become less clear to the point that you can no longer drive a vehicle or make out someone’s face.

Unfortunately, as Medical News Today explains, a bad enough case of cataracts is usually treated with surgery. So, whether or not you take corticosteroids orally or topically, if your eyesight starts to change, speak with your medical professional right away. They may be able to prescribe a different medication to treat your condition. Also, schedule an appointment with your eye doctor. But also keep in mind that cataracts can occur for a number of reasons besides as a side effect to medication.

This drug for treating bipolar disorder can turn your toes blue

Close-up of the bottom a person's feet

The image of blue toes usually conjures up thoughts of frostbite, or at the very least severe coldness. But a person can have what looks like frozen toes on the hottest day of the summer if they have an unexpected reaction to the drug lithium. And while their feet won’t feel cold, they may be painful. According to the Mayo Clinic, lithium is sometimes prescribed for bipolar disorder, also known as manic-depressive illness. This medication helps lessen the number of the mood swings (as well as their intensity) that are a common symptom of this ailment. How lithium does this is still not completely understood, although it does seem to involve the central nervous system. Regardless, someone taking lithium may be able to better manage bipolar disorder-related mania—but may also find both their fingers and their toes are sore and blue.

Luckily, this blue hue is one of the rarer side effects of lithium. Other uncommon side effects include becoming dizzy, experiencing headaches, and feeling discomfort in the eyes (via Mayo Clinic). Less rare (but still not common) side effects for lithium are an elevated or weaker pulse, fatigue, an increase in one’s weight, and loss of consciousness, among others. If you or someone you know is taking lithium and experiencing side effects, let the healthcare professional who prescribes it know, even if the lithium is helping with the mood fluctuations of bipolar disorder.

An antipsychotic drug may make it impossible to sit still

Ailments that affect someone physically can be difficult to manage, but the complexity of treating a condition is taken to a whole new level when it affects someone mentally and emotionally — and when the medications that can help come with side effects. Take, for example, the antipsychotic drug chlorpromazine, which is prescribed for bipolar disorder, schizophrenia, and other conditions that affect one’s mood and mental state (via WebMD). While this drug has been shown to help balance out the brain’s chemistry, which can help someone with a mental/mood disorder stay calmer, think more clearly, and not hallucinate, it also can make them feel restless. Specifically, someone taking an antipsychotic drug like chlorpromazine could experience a type of movement disorder known as akathisia (via WebMD). Someone with akathisia may fidget, walk in place, and constantly move their legs while they’re seated. Be sure to discuss your options with your doctor if you experience any of these symptoms while on chlorpromazine — they may be able to alter your medication or dosage to help relieve this side effect.

This antibiotic can have you seeing double

A blurred stop sign against a wooden and green background

From treating acne to curing the plague, tetracycline has a very impressive resume as far as antibiotics go. According to Medline Plus, this drug is used to neutralize the bacteria behind such ailments as Lyme disease, pneumonia, food poisoning, and infections throughout the body. However, like many other medications, tetracycline has its share of side effects, and some of them are quite serious.

As Medline Plus explains, this antibiotic can affect someone’s eyesight, causing them to see double. In addition, a person taking tetracycline may experience headaches, discomfort in their chest, and inflammation in their joints, as well as have problems breathing. And even months after discontinuing treatment, someone who took tetracycline may have cramps in their stomach or blood in their stool. All of these side effects are considered severe enough to require medical attention.

Additional side effects of tetracycline include diarrhea, vomiting, a sore throat, and swelling of the tongue. And like the proton pump inhibitors used to treat acid reflux disease, tetracycline (as well as other antibiotics) can also cause hairy tongue, a condition where a coating on the tongue makes it looks like it’s growing hair (via The American Academy of Oral Medication, Healthline and Medline Plus). Fortunately, hairy tongue is not dangerous and is usually only temporary. However, you should still contact your healthcare professional if you experience it.

Certain blood pressure medications can take away your sense of taste

Man happily eating a slice of pizza

If you or someone you know has high blood pressure, then you’ve probably heard the phrase "ACE inhibitors." ACE stands for angiotensin-converting enzyme, and as the name suggests, ACE inhibitors block these enzymes, which keeps your blood vessels from narrowing (via Medical News Today). This allows your blood to circulate more easily, helping keep your blood pressure from rising. However, like so many treatments, ACE inhibitors can have side effects, including losing one’s sense of taste. So, if you take a bite of your favorite snack but its flavor seems weak, it could be you’re experiencing a side effect of your blood pressure medicine. Other ones to watch for include a metal taste in your mouth, dizzy spells, headaches, and feeling drained. You also may experience diarrhea or constipation, or no longer feel as hungry as you normally would. The good news is these are not common side effects of this family of drugs. Most people who take ACE inhibitors only develop a dry cough.

Besides assisting with managing blood pressure, ACE inhibitors are also prescribed to help with other conditions such kidney disease caused by type 1 and type 2 diabetes (via Mayo Clinic). They are also used to treat post-heart attack patients for either a short or long period of time.

A muscle relaxer can help with heart burn

Woman with long hair in discomfort because she's experiencing heartburn

When we think about side effects from medicines, usually it’s the unpleasant ones that come to mind. But occasionally, a drug taken for one health issue might help with an entirely different one. Case in point, baclofen is showing promise for an ailment it was not designed to treat. As Verywell Health explains, baclofen is used to help relax muscles and prevent spasms that are the result of injuries, a stroke, or conditions like multiple sclerosis and cerebral palsy. However, an unintended side effect of baclofen is that it has the opposite effect on your lower esophageal sphincter, or LES. Okay, quick bio lesson: The LES is between your stomach and your esophagus, and normally it prevents stomach acid from flowing back up and causing unpleasant health problems like heartburn, acid reflux, and GERD (gastroesophageal reflux disease). But when your LES relaxes too much, acid escapes. And though it’s typically prescribed as a muscle relaxant, research is finding that baclofen may actually reduce how much your LES relaxes.

Despite promising data on this side effect, clinical testing by the pharmaceutical industry has not found a clear connection between taking baclofen and reducing the symptoms of GERD. However, some researchers have theorized that baclofen may only be effective against severe cases of acid reflux. If this is the case, then more targeted testing may be necessary to discern it’s full impact.

A common migraine medicine can turn your lips blue

Close-up of blue lips

Unless you’re a character in "X-Men" or trying out a novelty lipstick color, blue lips are usually not a good sign. But if you take a certain pain reliever, you could wind up with lips that look like you’ve been out in the cold too long. And that’s not the only part of you that may turn blue. According to WebMD, naproxen is commonly used to treat a number of health issues like tendonitis, headaches, arthritis, gout, bursitis, menstrual cramps, and stiffness in the joints. The reason it’s effective is that it reduces inflammation throughout the body, which in turn can help lessen pain. However, one of this drug’s potential — though rare – side effects is that it can turn your lips and nails blue (via Mayo Clinic). More commonly, it might cause bruising, itchy skin, tightness in your chest, indigestion or stomach pain, or your skin may develop purplish or blue patches. And though it’s sometimes prescribed to help headaches, naproxen can also cause them — so if you experience that as a side effect of taking this drug, you may want to speak to your doctor about making a switch.