Many things can affect how your body responds to a symptom and what kind of care you may need. These include:

• Your age. Babies and older adults tend to get sicker quicker.
• Your overall health. If you have a condition such as diabetes, HIV, cancer, or heart disease, you may need to pay closer attention to certain symptoms and seek care sooner.
• Medicines you take. Certain medicines, such as blood thinners (anticoagulants), medicines that suppress the immune system like steroids or chemotherapy, or natural health products can cause symptoms or make them worse.
• Recent health events, such as surgery or injury. These kinds of events can cause symptoms afterwards or make them more serious.
• Your health habits and lifestyle, such as eating and exercise habits, smoking, alcohol or drug use, sexual history, and travel.

Symptoms of infection may include:

• Increased pain, swelling, warmth, or redness in or around the area.
• Red streaks leading from the area.
• Pus draining from the area.
• A fever.

You can get dehydrated when you lose a lot of fluids because of problems like vomiting or fever.

Symptoms of dehydration can range from mild to severe. For example:

• You may feel tired and edgy (mild dehydration), or you may feel weak, not alert, and not able to think clearly (severe dehydration).
• You may pass less urine than usual (mild dehydration), or you may not be passing urine at all (severe dehydration).

Severe dehydration means:

• Your mouth and eyes may be extremely dry.
• You may pass little or no urine for 12 or more hours.
• You may not feel alert or be able to think clearly.
• You may be too weak or dizzy to stand.
• You may pass out.

Moderate dehydration means:

• You may be a lot more thirsty than usual.
• Your mouth and eyes may be drier than usual.
• You may pass little or no urine for 8 or more hours.
• You may feel dizzy when you stand or sit up.

Mild dehydration means:

• You may be more thirsty than usual.
• You may pass less urine than usual.

Severe dehydration means:

• The baby may be very sleepy and hard to wake up.
• The baby may have a very dry mouth and very dry eyes (no tears).
• The baby may have no wet diapers in 12 or more hours.

Moderate dehydration means:

• The baby may have no wet diapers in 6 hours.
• The baby may have a dry mouth and dry eyes (fewer tears than usual).

Mild dehydration means:

• The baby may pass a little less urine than usual.

If you're not sure if a fever is high, moderate, or mild, think about these issues:

With a high fever:

• You feel very hot.
• It is likely one of the highest fevers you've ever had. High fevers are not that common, especially in adults.

With a moderate fever:

• You feel warm or hot.
• You know you have a fever.

With a mild fever:

• You may feel a little warm.
• You think you might have a fever, but you're not sure.

Pain in adults and older children

• Severe pain (8 to 10): The pain is so bad that you can't stand it for more than a few hours, can't sleep, and can't do anything else except focus on the pain.
• Moderate pain (5 to 7): The pain is bad enough to disrupt your normal activities and your sleep, but you can tolerate it for hours or days. Moderate can also mean pain that comes and goes even if it's severe when it's there.
• Mild pain (1 to 4): You notice the pain, but it is not bad enough to disrupt your sleep or activities.

Pain in children under 3 years

It can be hard to tell how much pain a baby or toddler is in.

• Severe pain (8 to 10): The pain is so bad that the baby cannot sleep, cannot get comfortable, and cries constantly no matter what you do. The baby may kick, make fists, or grimace.
• Moderate pain (5 to 7): The baby is very fussy, clings to you a lot, and may have trouble sleeping but responds when you try to comfort him or her.
• Mild pain (1 to 4): The baby is a little fussy and clings to you a little but responds when you try to comfort him or her.

Certain health conditions and medicines weaken the immune system's ability to fight off infection and illness. Some examples in adults are:

• Diseases such as diabetes, cancer, heart disease, and HIV/AIDS.
• Long-term alcohol and drug problems.
• Steroid medicines, which may be used to treat a variety of conditions.
• Chemotherapy and radiation therapy for cancer.
• Other medicines used to treat autoimmune disease.
• Medicines taken after organ transplant.
• Not having a spleen.

Many prescription and non-prescription medicines can cause the skin to sunburn more easily. A few common examples are:

• Some antibiotics.
• Aspirin, ibuprofen (such as Advil or Motrin), and naproxen (such as Aleve).
• Skin products that contain vitamin A or alpha hydroxy acids (AHA).
• Some acne medicines.
• Some diabetes medicines that you take by mouth.

Symptoms of an allergic reaction may include:

• A rash, or raised, red areas called hives.
• Itching.
• Swelling.
• Trouble breathing.
• Mild belly pain or nausea.

Symptoms of heatstroke may include:

• Feeling or acting very confused, restless, or anxious.
• Trouble breathing.
• Sweating heavily, or not sweating at all (sweating may have stopped).
• Skin that is red, hot, and dry, even in the armpits.
• Passing out.
• Seizure.
• Nausea and vomiting.

Heatstroke occurs when the body can't control its own temperature and body temperature continues to rise.