An olfactory hallucination (phantosmia) makes you detect smells that aren't really present in your environment.

The odors detected in phantosmia vary from person to person and may be foul or pleasant. They can occur in one or both nostrils. The phantom smell may seem to always be present or it may come and go.

Phantosmia may occur after a head injury or upper respiratory infection. It can also be caused by temporal lobe seizures, inflamed sinuses, brain tumors and Parkinson's disease.

Consult your doctor if you experience the symptoms of phantosmia, so that your doctor can rule out any serious underlying disorders that may be causing the detected smell.

Parosmia is another smell disorder that's similar to phantosmia. But, in parosmia a smell that's present in your environment is distorted. Parosmia can occur with damage to the olfactory system, such as after a severe respiratory infection.

Phentermine (Adipex-P, Lomaira) is an amphetamine-like prescription medication used to suppress appetite. It can help weight loss by decreasing your hunger or making you feel full longer. Phentermine is also available in combination with topiramate for weight loss (Qsymia).

Like other prescription weight-loss drugs, phentermine is intended to be used as part of an overall weight-loss plan. It is indicated for people who are obese, and who have failed to lose enough weight with diet and exercise alone — not for people who want to lose just a few pounds.

Phentermine is a Schedule IV drug, a classification given to drugs that have a potential for abuse, although the actual potential appears to be low.

Common side effects of phentermine include:

• Increased heart rate
• Tingling or prickling feeling in hands or feet
• Dry mouth
• Sleeplessness
• Nervousness
• Constipation

Although phentermine is one of the most commonly prescribed weight-loss medications, it isn't a good option if you have heart disease, high blood pressure, an overactive thyroid gland or glaucoma. It also isn't for women who are pregnant, may become pregnant or are breast-feeding.

Phenylalanine isn't a health concern for most people. However, for people who have the genetic disorder phenylketonuria (PKU) or certain other health conditions phenylalanine can be a serious health concern.

Phenylalanine can cause intellectual disabilities, brain damage, seizures and other problems in people with PKU. Phenylalanine occurs naturally in many protein-rich foods, such as milk, eggs and meat. Phenylalanine is also sold as a dietary supplement.

The artificial sweetener aspartame (Equal, NutraSweet), which is added to many medications, diet foods and diet sodas, contains phenylalanine.

Federal regulations require that any beverage or food that contains aspartame bear this warning: "Phenylketonurics: Contains phenylalanine." This warning helps people with PKU avoid products that are a source of phenylalanine.

If you don't have PKU, you probably don't need to worry about harmful health effects of phenylalanine — with certain important exceptions. Aspartame in large doses can cause a rapid increase in brain levels of phenylalanine. Because of this, use products with aspartame cautiously if you:

• Take certain medications, such as monoamine oxidase inhibitors, neuroleptics or medications that contain levodopa (Sinemet, Rytary, others)
• Have the muscle movement disorder tardive dyskinesia
• Have a sleep disorder, anxiety disorder or other mental health condition; phenylalanine may worsen feelings of anxiety and jitteriness

If you aren't sure if phenylalanine or aspartame is a concern for you, talk to your doctor. A blood test to determine if you have PKU is available and is now routinely done as part of newborn screening.

Phosphatidylserine (fos-fuh-tie-dul-SER-een) is a dietary supplement that has received some interest as a potential treatment for Alzheimer's disease and other memory problems. Several studies with phosphatidylserine indicate improved cognitive abilities and behaviors. However, improvements lasted only a few months and were seen in people with the least severe symptoms.

Initially, phosphatidylserine supplements were derived from the brain cells of cows. But because of concerns about mad cow disease, most manufacturers now produce the supplements from soy or cabbage derivatives. Preliminary studies have shown that plant-based phosphatidylserine supplements may also offer benefits, but more research is needed. However, no modern studies have continued to focus on phosphatidylserine, suggesting its limited effect.

Keep in mind that the Food and Drug Administration doesn't require manufacturers to provide evidence of the potential risks and benefits of phosphatidylserine — or of any supplement. Consult your doctor before starting any dietary supplement.

Photodynamic therapy may play a limited role in lung cancer treatment — generally complementing, rather than replacing, other forms of treatment.

Photodynamic therapy may be an option for treating superficial non-small cell lung cancers that haven't spread beyond the lungs and those that are located in areas easily reached with the tools used during the treatment.

Photodynamic therapy begins with the injection of a light-sensitive medication into a vein. One to three days later, the doctor shines light of a certain wavelength onto the tumor from inside the body — typically using a thin, lighted tube called a bronchoscope, which is passed through the mouth into the lungs. The light destroys the cells that have absorbed the light-sensitive medication.

After photodynamic therapy, your whole body is sensitive to light. Generally you need to avoid any exposure to bright light, including the sun, for up to eight weeks after treatment.

Photodynamic therapy isn't effective for cancer that has spread beyond the lung or tumors that can't be reached by the bronchoscope.

During treatment for infectious pink eye (conjunctivitis), you'll be advised to temporarily stop wearing your contact lenses. It's OK to start wearing your contacts again once you've completed your antibiotics, your eye is no longer pink and you've had no discharge for 24 hours.

After treatment is complete, your doctor will likely recommend that you throw out contacts you've worn if your lenses are disposable. This can save you from getting a repeat infection.

If your lenses aren't disposable, disinfect them overnight before reusing them. Don't forget to double-check the expiration date on your lens disinfection solution to be sure it's still effective. Ask your doctor if you should discard and replace your contact lens accessories, such as the lens case used before or during the illness.

Pink eye (conjunctivitis) generally remains contagious as long as your child is experiencing tearing and matted eyes. Signs and symptoms of pink eye usually improve within three to seven days. Check with your doctor if you have any questions about when your child can return to school or child care.

Keep in mind that pink eye is no more contagious than the common cold. It's OK to return to work, school or child care if you're not able to take time off — just stay consistent in practicing good hygiene, including hand-washing after touching the eyes.

Good question. You wouldn't want this act of kindness to have unintended and even deadly consequences for someone who is hospitalized.

Here are some general guidelines to consider before you bring a meal or special treat to the hospital:

• Before you bring food in, check with the nurse, doctor or dietitian. Your loved one may be at risk of infection or may need to follow a very strict diet. In some situations, even normal bacteria in foods (such as uncooked items like fruits or salads) or excess nutrients (such as those containing vitamin K, or unknown substances like gluten or allergens) can be dangerous.
• If you get the OK to bring food in, make sure you prepare food safely. The Department of Agriculture has excellent information on its website about food safety for people who are vulnerable to infection. Throughout the steps of food preparation, it's important to follow the mantra:
1. Clean. Wash your hands, utensils and cutting boards before and after contact with raw meat, poultry, seafood and eggs.
2. Separate. Keep raw meat, poultry and seafood away from foods that won't be cooked.
3. Cook. Use a food thermometer — you can't tell food is cooked safely by how it looks.
4. Chill. Refrigerate foods within two hours and keep the fridge at 40 F or below.
• Bring only enough food that can be eaten at one time. Consider single-serve items, such as individual yogurts, packages of crackers and peanut butter, and wrapped cookies. That way there are no leftovers to worry about.
• Don't store perishable foods in the room. In addition to being unsafe, they can be unappetizing.
• Label all food items. Put the name of your loved one on the food container and the date that the food was prepared. You don't want your kind intention causing problems for another patient.

These are basic guidelines. It's a good idea to check with the hospital you're visiting to see if it has more-specific requirements.

With plugged ears, your eustachian tubes — which run between your middle ear and the back of your nose — become obstructed. You may experience a feeling of fullness or pressure in your ears. You may also have ear pain, dizziness and muffled hearing. As swelling from the cold subsides, the obstruction usually resolves.

If your ears are plugged, try swallowing, yawning or chewing sugar-free gum to open your eustachian tubes. If this doesn't work, take a deep breath and try to blow out of your nose gently while pinching your nostrils closed and keeping your mouth shut. If you hear a popping noise, you know you have succeeded.

Other options for clearing plugged ears may include:

• Nasal decongestants, but for no more than a few days
• Topical nasal steroids, especially in people with allergies
• Ventilation tubes, in severe cases, to drain fluid and relieve pressure

Call your doctor if your symptoms are severe or last more than two weeks.

Poinsettia plants are less toxic than once believed.

In most cases, poinsettia exposure causes only discomfort, including:

• A mild, itchy rash. Skin contact with the sap of a poinsettia plant can cause a rash. If this happens, wash the affected area with soap and water. Apply a cool compress to ease itching.
• A mild stomachache, vomiting or diarrhea. This can happen after eating part of a poinsettia plant. Severe signs and symptoms are unlikely. If you find a child eating a poinsettia plant, clear and rinse his or her mouth.
• Eye irritation. If the sap of a poinsettia plant comes in contact with the eyes, they can become red and irritated. If this happens, flush the eyes with water.
• Allergic reaction. Some people are more sensitive to poinsettia plants than are others. Reactions to poinsettia plants are more common among people who have latex allergies, since latex and poinsettia plants share several proteins. Also, if you're allergic to avocados, bananas, chestnuts, kiwis and passion fruits you might have a greater chance of being allergic to poinsettia plants. In case of a severe reaction, seek prompt medical attention.