Understanding Sodium Cromoglicate (Cromolyn Sodium)
Discovered in 1965 by researcher Roger Altounyan, sodium cromoglicate (also called cromolyn sodium) marked a new approach to managing asthma and other allergic diseases [1.5.3, 1.6.1]. It belongs to a class of drugs known as mast cell stabilizers [1.8.4]. Unlike antihistamines, which block the action of histamine after it has been released, sodium cromoglicate works proactively. It stabilizes the membranes of mast cells, preventing them from releasing histamine and other inflammatory mediators that cause allergic symptoms [1.3.2, 1.10.1]. This preventative action makes it particularly useful for prophylaxis, meaning it is often used to prevent symptoms before they start [1.8.3]. The medication is considered very safe, with a low incidence of side effects [1.6.1]. It is available in several different formulations, each targeting a specific condition [1.8.3].
Mechanism of Action: How It Prevents Allergic Reactions
An allergic reaction is triggered when the immune system overreacts to a harmless substance called an allergen, such as pollen, dust mites, or pet dander [1.8.4]. This response involves an antibody called Immunoglobulin E (IgE). When IgE on the surface of mast cells encounters an allergen, it causes these cells to degranulate—a process where they release a flood of chemicals like histamine and leukotrienes [1.3.2, 1.8.4]. These chemicals are responsible for the classic allergy symptoms: itching, swelling, runny nose, and watery eyes [1.5.1].
Sodium cromoglicate's primary role is to inhibit this degranulation process [1.10.1]. By stabilizing the mast cell membrane, it stops the release of these inflammatory mediators when challenged by an allergen [1.3.4]. This action helps prevent both the immediate and late-phase reactions of an allergic response, making it effective for long-term management rather than for treating acute, already-present symptoms [1.3.3, 1.10.1].
Primary Uses and Formulations of Sodium Cromoglicate
Sodium cromoglicate is formulated in different ways to treat specific areas of the body. The form of the medication determines its primary use.
Allergic Conjunctivitis (Eye Drops)
For eye allergies, which cause redness, itching, puffiness, and watery eyes, sodium cromoglicate is available as ophthalmic eye drops [1.7.4]. It is considered a first-line agent for treating these symptoms, which are often triggered by hay fever, dust mites, and other environmental allergens [1.7.1, 1.7.4].
- How it's used: Typically, one or two drops are administered into each eye four times daily [1.11.4]. For seasonal allergies, it is most effective when started before the pollen season begins and used regularly throughout [1.7.2].
- Brand Names: Common brands include Opticrom, Allercrom, Catacrom, and Murine Hayfever Relief [1.4.1].
- Key Consideration: While the eye drops can relieve symptoms, they may cause temporary stinging or burning upon application [1.7.1].
Allergic Rhinitis (Nasal Spray)
Sodium cromoglicate nasal spray (brand name Nasalcrom) is an over-the-counter treatment for nasal allergies [1.8.4]. It is used to prevent and relieve symptoms like sneezing, runny nose, itching, and nasal congestion associated with hay fever, pet, and dust allergies [1.8.2, 1.8.4]. For best results, use should begin before exposure to an allergen [1.8.4]. It may take one to four weeks of regular use to feel the full effects [1.8.2]. Studies have shown it can significantly improve nasal symptoms, particularly nasal obstruction [1.8.1].
Prophylaxis of Asthma (Inhaled Solution)
Inhaled sodium cromoglicate is used as a maintenance therapy to prevent mild to moderate bronchial asthma attacks, particularly those induced by allergens or exercise [1.6.1, 1.6.3]. It is not a bronchodilator and should not be used to treat an acute asthma attack that has already started [1.5.3]. Its effectiveness in asthma management is due to its ability to prevent both early and late asthmatic responses to allergens [1.3.4]. While it has been a cornerstone of asthma therapy for decades, some modern guidelines suggest it is less effective than inhaled corticosteroids, which are now often the first choice [1.6.1, 1.8.3].
Systemic Mastocytosis and Food Allergies (Oral Solution)
Oral cromolyn sodium (brand name Gastrocrom) is prescribed to manage the symptoms of mastocytosis, a rare condition characterized by an excessive number of mast cells in the body [1.9.3]. These mast cells can cause symptoms like abdominal pain, diarrhea, nausea, vomiting, headache, skin flushing, and itching [1.5.1, 1.9.2]. The oral solution works by stabilizing the mast cells in the gut [1.5.4]. It's typically taken as a liquid mixed with water about 30 minutes before meals and at bedtime [1.9.3]. It may take two to three weeks to see a benefit [1.5.4]. It also has some off-label use for food allergies [1.8.3].
Comparison with Other Allergy Medications
Sodium cromoglicate has a unique place among allergy treatments. The table below compares it to two other common classes of allergy medication.
| Feature | Sodium Cromoglicate | Antihistamines | Nasal Corticosteroids |
|---|---|---|---|
| Mechanism | Mast cell stabilizer; prevents histamine release [1.3.2]. | Blocks histamine from binding to its receptors after release [1.8.4]. | Reduces inflammation and swelling in nasal passages [1.8.4]. |
| Primary Use | Prophylactic (preventative) treatment for allergies and asthma [1.6.1, 1.8.4]. | Quick relief of acute allergy symptoms (sneezing, itching, runny nose) [1.8.4]. | Long-term management of nasal allergy symptoms; highly effective for congestion [1.8.4]. |
| Onset of Action | Slower; may take days to weeks for full effect [1.3.2, 1.8.2]. | Fast-acting for immediate symptom relief [1.10.3]. | Slower onset than antihistamines, but longer-lasting effects [1.8.4]. |
| Best For | Preventing symptoms before they start; long-term, safe management [1.6.1]. | Treating symptoms as they occur [1.8.4]. | Controlling persistent or moderate-to-severe nasal symptoms [1.8.4]. |
Safety and Side Effects
Sodium cromoglicate is generally well-tolerated with a strong safety profile [1.6.1]. Side effects are typically mild, transient, and related to the application site.
- Inhaled: Coughing or throat irritation may occur. Rinsing the mouth with water after use can help [1.5.2].
- Eye Drops: Temporary stinging or burning in the eyes is a common side effect [1.7.1].
- Nasal Spray: Sneezing or nasal irritation can happen [1.5.2].
- Oral: The most frequently reported adverse events are headache and diarrhea [1.5.2, 1.5.3].
Serious allergic reactions are rare [1.5.1]. In terms of special populations, sodium cromoglicate eye drops are considered safe for use during pregnancy and breastfeeding, as very little of the drug is absorbed into the bloodstream [1.11.1, 1.11.2, 1.11.3].
Link: Learn more about sodium cromoglicate from the NHS
Conclusion
Sodium cromoglicate is a versatile and safe mast cell stabilizer used to prevent and manage a range of allergic conditions. Its primary strength lies in its prophylactic nature—by stopping allergic reactions before they start, it provides effective control of allergic conjunctivitis, rhinitis, and the gastrointestinal symptoms of mastocytosis, and serves as a maintenance therapy for mild asthma. While not intended for acute symptom relief, its excellent safety profile makes it a valuable option for long-term management of allergies, including for children and during pregnancy.
