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.

Major trauma is any event that can cause very serious injury, such as:

• A fall from more than 3.1 m (10 ft)[more than 1.5 m (5 ft) for children under 2 years and adults over 65].
• A car crash in which any vehicle involved was going more than 32 km (20 miles) per hour.
• Any event that causes severe bleeding that you cannot control.
• Any event forceful enough to badly break a large bone (like an arm bone or leg bone).

With severe bleeding, any of these may be true:

• Blood is pumping from the wound.
• The bleeding does not stop or slow down with pressure.
• Blood is quickly soaking through bandage after bandage.

With moderate bleeding, any of these may be true:

• The bleeding slows or stops with pressure but starts again if you remove the pressure.
• The blood may soak through a few bandages, but it is not fast or out of control.

With mild bleeding, any of these may be true:

• The bleeding stops on its own or with pressure.
• The bleeding stops or slows to an ooze or trickle after 15 minutes of pressure. It may ooze or trickle for up to 45 minutes.

Pain in children 3 years and older

• Severe pain (8 to 10): The pain is so bad that the child can't stand it for more than a few hours, can't sleep, and can't do anything else except focus on the pain. No one can tolerate severe pain for more than a few hours.
• Moderate pain (5 to 7): The pain is bad enough to disrupt the child's normal activities and sleep, but the child can tolerate it for hours or days.
• Mild pain (1 to 4): The child notices and may complain of the pain, but it is not bad enough to disrupt his or her 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.

When an area turns blue, very pale, or cold, it can mean that there has been a sudden change in the blood supply to the area. This can be serious.

There are other reasons for colour and temperature changes. Bruises often look blue. A limb may turn blue or pale if you leave it in one position for too long, but its normal colour returns after you move it. What you are looking for is a change in how the area looks (it turns blue or pale) and feels (it becomes cold to the touch), and this change does not go away.

Shock is a life-threatening condition that may occur quickly after a sudden illness or injury.

Babies and young children often have several symptoms of shock. These include:

• Passing out (losing consciousness).
• Being very sleepy or hard to wake up.
• Not responding when being touched or talked to.
• Breathing much faster than usual.
• Acting confused. The child may not know where he or she is.

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.

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

• Diseases such as diabetes, cystic fibrosis, sickle cell disease, and congenital heart disease.
• Steroid medicines, which are used to treat a variety of conditions.
• Medicines taken after organ transplant.
• Chemotherapy and radiation therapy for cancer.
• Not having a spleen.