An acute condition is one where symptoms appear suddenly and worsen rapidly, while a chronic condition is one that develops gradually and worsens over an extended period of time.
Acute pain tells your body you’ve been hurt, say when you fall, stub a toe, burn your finger etc. It appears suddenly, peaks as a signal to your body to heal the injury, and wanes away as it heals before it finally disappears completely once the injury is healed. Similarly, acute illnesses like flu, common cold etc. come unwarned, worsen and disappear.
Chronic pain, on the other hand creeps up on you gradually, and by the time you feel its presence, you realize it has been there for a while. It lasts for weeks, even months beyond the expected recovery, till you feel the pain itself is a disease and becomes a part of you. A back pain that lasts for months and worsens over time is a good example of chronic pain.
Examples of acute conditions include a broken bone or an asthma attack, a burn, and a neck injury while playing. Acute diseases include colds, flu and strep. Acute pain is experienced after someone has been hurt, for example a cut or broken bone.
Many illnesses can occur in both acute or chronic form. For example, acute renal failure occurs when an event, such as dehydration, blood loss or taking medicines, leads to kidney malfunction. Chronic kidney disease, however, is caused by long-term conditions, such as high blood pressure or diabetes, and involves the gradual damage of the kidneys over time.
A condition is typically only diagnosed as chronic when symptoms have been present for at least three months, especially in the case of acute or chronic pain.
edit Acute vs Chronic Pain
Dr. Fennel of Hand and Foot Clinic of America explains briefly the difference between acute and chronic pain.
Acute illnesses are far more common than chronic illnesses. An acute condition can be as simple as a stubbed toe, or as serious as a heart attack. They are simply illnesses or injuries that occur and end relatively quickly.
Over 90 million Americans have a chronic illness. Approximately 1 in 3 people are affected by chronic illness.
Chronic diseases often require extended care or hospitalization. For example, someone with chronic kidney disease may require medication and dialysis regularly. Chronic pain conditions such as migraines, back pain or asthma may sometimes be treated with a dedicated diet and/or fitness routine. Chronic diseases can often not be cured. However, treatment may reduce the symptoms.