Systemic Reaction Throughout the Body

When a reaction stays with one area of the body, it's known as a localized reaction. When inflammation spreads from a localized area of one organ (like the skin) to other organ systems in the body, it's known as a systemic reaction. The inflammation can be from toxins, allergies or infections.

Woman scratching shoulder and neck
RyanKing999 / Getty Images

Anaphylaxis (Allergies)

Anaphylaxis is a systemic reaction related to allergies. It occurs when an allergic reaction moves from a single organ system (most commonly the integumentary system, which is the skin) to include at least one other system. Anaphylaxis often affects the respiratory system (shortness of breath) or the circulatory system (low blood pressure/shock) in addition to the integumentary system (itching, redness, and ​hives). Anaphylactic shock is a life-threatening, systemic allergic reaction characterized by dangerously low blood pressure.

Sepsis (Infection)

When an otherwise low-key bacterial infection develops into a full-body failure of organs, it's known as sepsis or septic shock. As healthcare providers learn more about sepsis and more about how we can treat it, recognition of this systemic disorder becomes increasingly important.Sepsis usually starts out as a common infection with typical signs and symptoms. Eventually, sepsis evolves into fatigue, confusion, no fever, weakness and progresses to low blood pressure.


Poisons or toxins often cause localized rashes or swelling. However, if they are picked up in the bloodstream or otherwise transported around the body, some toxins can cause reactions in areas far away from where the substance entered the body. Carbon monoxide poisoning, for example, shows signs and symptoms throughout the body. Fatigue, weakness, confusion, headaches, and nausea are all symptoms. In extreme cases, carbon monoxide poisoning can make the patient's skin very red.


There is no specific treatment for a systemic reaction. It is dependent on the type of reaction (allergic, toxic or septic). The important thing is to recognize a systemic reaction quickly and to seek help immediately. Not all systemic reactions are life-threatening, but when infection or a substance can affect so many different organ systems at the same time, chances are the outcome will not be desirable. It is important to avoid the known causes of reaction.

If you suspect a patient (or you) is experiencing a systemic reaction, head to the doctor or call 911 immediately. Try not to drive if you are experiencing symptoms of fatigue, confusion, dizziness or weakness. You might discover that you're not able to operate a motor vehicle safely for you or for others on the road.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Reber LL, Hernandez JD, Galli SJ. The pathophysiology of anaphylaxis. J Allergy Clin Immunol. 2017;140(2):335-348. doi:10.1016/j.jaci.2017.06.003

  2. Rello J, Valenzuela-sánchez F, Ruiz-rodriguez M, Moyano S. Sepsis: A Review of Advances in Management. Adv Ther. 2017;34(11):2393-2411. doi:10.1007/s12325-017-0622-8

  3. Eichhorn L, Thudium M, Jüttner B. The Diagnosis and Treatment of Carbon Monoxide Poisoning. Dtsch Arztebl Int. 2018;115(51-52):863-870. doi: 10.3238/arztebl.2018.0863

By Rod Brouhard, EMT-P
Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients.