A fever isn\u2019t always a problem. Defined as a temporary increase in body temperature, a fever is just a symptom, not an illness.\nIn fact, sometimes a fever can be a good thing: It\u2019s often a sign that your body is fighting an infection or illness. But how do you know when a fever is dangerous? When is it time to see a doctor for a high temperature?\nWhy You Have a Fever\nA fever typically occurs in response to infection, when your body\u2019s immune system is fighting off bacteria or a virus. People with autoimmune conditions (in which the body\u2019s immune system attacks itself) can also experience fevers. Common causes of fever include:\n\nColds and flu\nEar infections\nSinus infections\nBronchitis\nPneumonia\nSkin infections\nBladder and urinary-tract infections\nAppendicitis\nBlood clots\nRheumatoid arthritis\nLupus\nInflammatory bowel disease\nCancer, especially lymphoma and leukemia\n\nIn children, teething and immunizations may cause a slight fever for a day or two.\nWhen to Seek Help: How to Know When a Fever Is Dangerous\nYou should seek medical attention for yourself or a child under the following fever scenarios:\n\nIf your child is 3 months old or younger and has a rectal temperature of 100.4 degrees F or higher\nIf your child is 3 to 12 months old and has an oral temperature of 102.2 degrees F\nIf your child is 2 years old or younger and has a fever that lasts longer than 24 to 48 hours\nAdults with a fever higher than 105 degrees F or a fever over 103 degrees F that rises or lasts longer than 48 hours\n\nIn addition, you should seek medical care if you have a fever accompanied by rash and bruising, difficulty breathing, and\/or pain while urinating. Also consult a doctor if you have recently been vaccinated, visited another country, or have a serious pre-existing illness. Seek out a pediatrician if your child seems confused, has a stiff neck, and\/or won\u2019t stop crying.\n\nThe Basics of Body Temperature\nNormal body temperature is 98.6 degrees Fahrenheit, and anything above 99.5 F (when measured orally with a thermometer) is considered a fever in both children and adults.\nYour body temperature can rise naturally throughout the day and is usually higher in the evening. A number of other factors can increase body temperature, but these factors are not considered fever-inducing. Things like physical exertion, heavy clothing, high humidity and heat, strong emotions, and certain medications can trigger your body temperature to rise. If you\u2019re a woman on your menstrual cycle you may also experience a higher body temperature.\nHow to Lower a Fever\nFor most adults and kids with a mild fever under 102 degrees F, rest is the best solution. You can try to lower the fever yourself with some simple steps that work for both children and grownups:\n\nRemove heavy clothing and blankets and keep surroundings cool but not cold\nTake a lukewarm bath\nTake acetaminophen as directed, but do not give young children aspirin\nDrink plenty of fluids\nAvoid ice baths and alcohol rubs, which can cause shivering and in turn raise body temperature further\n\nContact your\u00a0primary care physician\u00a0or visit a\u00a0UPMC Urgent Care location\u00a0if your fever persists.