How Leukotrienes Drive Chronic Inflammation?

Leukotrienes are signaling molecules your immune system makes from fats in cell membranes. When this system stays switched on, it keeps calling immune cells into tissue and keeps blood vessels leaky, which is how it drives chronic inflammation. That process sits behind asthma, allergic rhinitis, and several other long-term inflammatory conditions.

The name comes from where they were first found. Leukocytes are white blood cells, and these molecules each contain three double bonds, called trienes. Researchers identified them in the late 1970s, and the work earned a Nobel Prize in Physiology or Medicine in 1982. Since then, leukotrienes have become one of the better-understood arms of the inflammatory response, partly because drugs that block them already exist and are widely used.

What Are Leukotrienes and Where Do They Come From?

Leukotrienes are made from arachidonic acid, a fatty acid that sits inside the phospholipid layer of your cell membranes. When a cell is activated, an enzyme called phospholipase A2 releases arachidonic acid. From there, a second enzyme, 5-lipoxygenase, starts converting it into leukotrienes.

This is important because it explains why leukotrienes and certain pain-relief drugs do not overlap. Aspirin and ibuprofen work on a different branch of arachidonic acid metabolism, the cyclooxygenase pathway, which produces prostaglandins. Blocking that pathway does not block leukotrienes. The two systems run in parallel off the same starting material.

The main cell types that produce leukotrienes are mast cells, eosinophils, neutrophils, macrophages, and basophils. These are all immune cells. That is not a coincidence. Leukotrienes are essentially a local alarm system that immune cells use to communicate with each other and with nearby tissue.

There are two broad families. Cysteinyl leukotrienes (LTC4, LTD4, LTE4) contain the amino acid cysteine and act mainly on airways and blood vessels. Leukotriene B4 (LTB4) is structurally different and acts mainly as a magnet for neutrophils, a type of white blood cell.

How Do Leukotrienes Drive Chronic Inflammation?

Chronic inflammation is not just inflammation that lasts a long time. It is inflammation that fails to resolve. Leukotrienes contribute to that failure in several specific ways.

First, they recruit immune cells into tissue. LTB4 is one of the strongest known signals for drawing neutrophils out of the bloodstream and into a site of injury or irritation. In short bursts this is helpful. When the signal does not stop, tissue fills with immune cells that keep releasing more inflammatory mediators.

Second, cysteinyl leukotrienes make blood vessels leak. They cause smooth muscle in the vessel wall to contract and the lining to become more permeable, so plasma and fluid move into surrounding tissue. This is part of why leukotriene-driven conditions produce swelling and mucus.

Third, they tighten airway smooth muscle. Cysteinyl leukotrienes are among the most potent bronchoconstrictors the body produces. In people with asthma, this contributes directly to wheezing and shortness of breath.

Fourth, they increase mucus production in the airways. Excess mucus narrows already-tight airways and is difficult to clear.

Fifth, and less often discussed, leukotrienes help sustain the inflammatory cycle itself. They activate immune cells that then produce more leukotrienes. That feedback loop is one reason chronic inflammatory conditions can persist even when the original trigger is gone.

This is the key insight: leukotrienes are not a one-time signal. They are part of a self-reinforcing loop, and interrupting that loop is what leukotriene-blocking drugs are designed to do.

Which Conditions Are Linked to Leukotrienes?

Asthma is the condition most clearly tied to leukotrienes. Cysteinyl leukotrienes are found in higher amounts in the airways of people with asthma, and drugs that block their action reduce symptoms in many patients.

Allergic rhinitis, the stuffy, runny nose that comes with seasonal allergies, also involves cysteinyl leukotrienes. They contribute to nasal congestion and mucus production after allergen exposure.

Other conditions with a documented leukotriene component include:

• Aspirin-exacerbated respiratory disease, where people react badly to aspirin and other NSAIDs
• Exercise-induced bronchoconstriction, where airways narrow during or after physical activity
• Chronic urticaria, a form of persistent hives
• Some forms of inflammatory bowel disease, where LTB4 is elevated in affected tissue
• Certain skin conditions, including atopic dermatitis

In each case, the evidence for leukotriene involvement varies. Asthma and allergic rhinitis have the strongest support. For other conditions, the picture is less clear, and blocking leukotrienes does not always produce meaningful symptom relief even when levels are elevated.

How Are Leukotrienes Blocked in Treatment?

Two classes of drugs target this pathway. One class blocks the enzyme that makes leukotrienes. The other blocks the receptor that cysteinyl leukotrienes bind to.

Montelukast and zafirlukast are receptor blockers. They attach to the CysLT1 receptor so cysteinyl leukotrienes cannot dock and trigger a response. Zileuton works differently. It inhibits 5-lipoxygenase, the enzyme that starts leukotriene production, so fewer leukotrienes are made in the first place.

These drugs are used mainly in asthma and allergic rhinitis. They are generally taken as a daily pill. They are not rescue medications. They do not relieve an attack in progress and should not be used that way.

Their effectiveness varies. In asthma, they tend to work better in people with allergic asthma and in those with exercise-induced symptoms. In many patients they are less effective than inhaled corticosteroids, which remain the standard first-line controller medication for persistent asthma. Some clinicians use leukotriene modifiers as an add-on rather than a first choice.

There are also safety considerations. In 2020, the US Food and Drug Administration added a boxed warning to montelukast about serious neuropsychiatric events, including agitation, depression, sleep disturbances, and suicidal thoughts. The agency advised weighing benefits and risks, particularly in people with existing mental health conditions. Anyone taking these medications who notices mood or behavior changes should contact their prescriber.

Can Diet or Lifestyle Affect Leukotriene Production?

Because leukotrienes are made from arachidonic acid, an omega-6 fatty acid, it is reasonable to ask whether diet changes how much your body produces. The answer is more complicated than most online sources suggest.

Some research suggests that omega-3 fatty acids from fish oil can shift the balance of fatty acid substrates away from arachidonic acid, leading to production of less inflammatory mediators. This has been studied in asthma and other conditions. Results have been mixed. Some trials show small improvements in symptoms, others show none. No clinical guideline currently recommends fish oil as a primary treatment for leukotriene-driven disease.

Dietary changes do not replace medication for conditions like asthma. Anyone considering dietary approaches should discuss them with their clinician rather than adjusting treatment on their own.

There is also a common misconception worth addressing. Many supplements marketed for “inflammation” claim to block leukotrienes. Most have not been tested in controlled human trials for that specific mechanism. A few compounds, such as certain flavonoids found in fruits and vegetables, have shown 5-lipoxygenase inhibition in laboratory studies. Whether that translates to meaningful effects in the human body at typical dietary or supplemental doses is largely unknown.

Omega-6 fats are not the problem on their own. Arachidonic acid is a normal, necessary part of cell membranes and is involved in many processes beyond leukotriene production. The issue in chronic inflammation is regulation, not the presence of the raw material.

What Makes Leukotrienes Different From Other Inflammatory Signals?

Leukotrienes are not the only molecules driving inflammation. Histamine, prostaglandins, cytokines, and others all play roles. What sets leukotrienes apart is their combination of potency and duration.

Histamine acts fast and fades quickly. It is why an allergic reaction can flare within minutes and settle within an hour. Leukotrienes act more slowly but their effects last longer. This is part of why leukotriene-driven symptoms, like the nasal congestion of allergic rhinitis, tend to be the persistent component rather than the sudden sneeze.

Prostaglandins overlap with leukotrienes in some functions but come from a different enzymatic branch. Blocking prostaglandins with NSAIDs does nothing to leukotrienes. In fact, in some people with aspirin sensitivity, blocking the prostaglandin pathway can shift more arachidonic acid toward leukotriene production, which is one proposed explanation for why NSAIDs trigger reactions in that group.

Cytokines are a broader category of immune signaling proteins. They influence leukotriene production and are influenced by it. The relationship is bidirectional, not a simple chain of command.

Understanding these distinctions matters because it explains why different anti-inflammatory drugs work for different conditions. There is no single inflammation pathway. There are several, and leukotrienes are one well-characterized piece of a larger system.