Dismiss Modal

Types

Idiopathic Environmental Intolerance (IEI)

Choose a preferred language


What is IEI?

Idiopathic environmental intolerance (IEI) is a set of symptoms caused by contact with some kinds of substances. It used to be known as multiple chemical sensitivity (MCS). People with IEI have symptoms when exposed to low levels of common substances. Symptoms can include fast heart rate, sweating, and feeling dizzy.


What causes IEI?

Researchers are doing studies to learn the causes of IEI. It's not an allergic reaction. It does not cause the release of chemicals by the immune system. A physical cause is hard to find. Because of this, some studies suggest IEI may be linked to psychiatric disorders. These include somatoform disorders, depression, and anxiety. IEI occurs more often in women than in men. IEI happens more often in people in their 30s or 40s.


Triggers

Substances that cause symptoms are called triggers. These may be synthetic or natural substances. Reported triggers include:

  • Caffeine

  • Food additives

  • Carpet and furniture odors

  • Perfumes and scented products

  • Paint

  • Cigarette smoke

  • Vehicle exhaust, fuel odors

  • Pesticides and herbicides

  • Mobile telecommunication devices


Symptoms

People with IEI may have symptoms such as:

  • Increased heart rate, palpitations

  • Chest pain

  • Sweating

  • Shortness of breath

  • Fatigue

  • Dizziness

  • Warmth and redness of the face and neck (flushing)

  • Nausea

  • Trouble concentrating

  • Cough

  • Numbness


Treatment

Treatment for IEI may include:

  • Staying away from triggers

  • Counseling that may include cognitive behavioral therapy (CBT)

  • Medicines for some symptoms

© 2000-2025 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.

Find a doctor that's right for you.

From routine check-ups to groundbreaking treatments and beyond, Crestner Health is here to help you live your healthiest life.

Search our doctors
Related Articles
Read article
Allergies
Allergic Bronchopulmonary Aspergillosis (ABPA)

Allergic bronchopulmonary aspergillosis (ABPA) means you are having an allergic reaction to a common fungus called Aspergillus. ABPA causes the lungs to become inflamed. This leads to symptoms, such as wheezing and coughing.

Read article
Allergies
Food Allergies

Detailed information on food allergies, including symptoms, diagnosis, and treatment.

Read article
Allergies
Allergic Rhinitis

Allergic rhinitis is an allergic reaction that affects the nose and often the eyes. Common indoor allergens include house dust mites, mold, cockroaches, and pet dander. Outdoor allergens include pollen from trees, grasses, and weeds.

Read article
Allergies
Allergen: Insect Stings

Detailed information on allergic reactions to insect bites and stings.