Understanding What Vitamin Deficiency Causes Dry Eyes and Mouth

October 29, 2025 •

4 min read

According to the World Health Organization, vitamin A deficiency is the leading cause of preventable childhood blindness worldwide. It is also a key answer to the question: what vitamin deficiency causes dry eyes and mouth? However, other nutrient deficits and underlying conditions can also be culprits.

Quick Summary

Several nutritional deficiencies can lead to dryness in the eyes and mouth. While vitamin A deficiency is a primary suspect for eye issues, B-complex vitamins, vitamin D, and other nutrients also play a role in maintaining moist mucous membranes. This guide explores the specific deficiencies and non-nutritional causes behind these symptoms, along with treatment options.

Key Points

Vitamin A is a primary suspect: A deficiency in vitamin A can cause xerophthalmia, a dry eye condition, by impairing the production of moisture needed to lubricate the cornea.
B vitamins affect nerve health and mucosa: Vitamin B12 deficiency is linked to dry, burning eyes and eye pain by potentially damaging corneal nerves, while other B vitamins affect the health of oral mucous membranes.
Vitamin D moderates inflammation: Low levels of vitamin D are associated with increased dry eye symptoms and poorer tear quality due to its role in regulating inflammation.
Autoimmune diseases are a major cause: Beyond vitamins, autoimmune conditions like Sjögren's syndrome are known to cause chronic dry eyes and mouth by attacking moisture-producing glands.
Medication side effects are common: Many prescription drugs, such as antidepressants and antihistamines, can cause dryness as a frequent side effect.
Diet and lifestyle play a role: Factors like poor hydration, smoking, and unbalanced diets can contribute to dryness and complicate symptoms.

Key Nutritional Deficiencies Linked to Dryness

While multiple factors can cause dry eyes and mouth, certain vitamin and mineral deficiencies are known to disrupt the normal function of moisture-producing glands.

Vitamin A

Vitamin A is arguably the most critical vitamin for eye health. A deficiency can cause a group of conditions known as xerophthalmia, a Greek term for 'dry eye'.

How it works: Vitamin A is essential for the production of moisture that lubricates the cornea, the outermost layer of the eye. It is also crucial for maintaining healthy mucous membranes in both the eyes and mouth.
Symptoms: Early signs of vitamin A deficiency include night blindness, followed by dry, dull-looking eyes (conjunctival xerosis). This can progress to more severe corneal damage and even blindness if left untreated.
Dietary sources: Good sources include liver, eggs, milk, and fortified foods. Beta-carotene, a precursor to vitamin A, is found in colorful fruits and vegetables like carrots, sweet potatoes, and leafy greens.

B-Complex Vitamins

Several B vitamins contribute to nerve health and the well-being of mucosal tissues, and deficiencies can impact moisture production.

Vitamin B12: A deficiency in vitamin B12 has been linked to severe dry eye and eye pain. Research suggests that supplementing with B12, often alongside artificial tears, can help repair the corneal nerve layer, reducing the burning sensation associated with dryness. A lack of B12 can also cause mouth sores and a sore tongue.
Vitamin B2 (Riboflavin): Insufficient riboflavin can damage the eyes' cells and lead to inflammation. A deficiency is also a known cause of mouth sores and a swollen, inflamed tongue.
Vitamin B3 (Niacin): Low niacin levels can be associated with bad breath, mouth sores, and a painful, inflamed tongue.

Vitamin D

Emerging research highlights the connection between vitamin D and dry eye disease, often linked to its anti-inflammatory properties.

How it works: Vitamin D plays a role in regulating immune responses and inflammation, which are contributing factors to dry eye syndrome. Lower levels of vitamin D are often correlated with increased dry eye symptoms and poorer tear quality.
Symptoms: Vitamin D deficiency has been linked to burning mouth syndrome, which includes a dry mouth sensation, along with a metallic taste.
Dietary sources: Sunlight is the primary source, but dietary intake can come from fatty fish (salmon, mackerel), fortified milk, and egg yolks.

Other important nutrients

While not vitamins, certain minerals also contribute to the health of mucous membranes.

Iron: An iron deficiency can lead to an inflamed tongue, mouth sores, and dry mouth.
Zinc: Zinc assists in saliva production and can influence the composition of saliva, which is vital for protecting against dental problems.

Comparison of Vitamin Deficiencies and Their Impact on Dryness


Nutrient	Primary Symptom(s)	Mechanism of Action	Common Sources
Vitamin A	Dry eyes (xerophthalmia), night blindness, corneal damage	Maintains the health of mucous membranes and supports moisture production in the eyes.	Liver, eggs, dairy, carrots, sweet potatoes, spinach.
Vitamin B12	Dry, burning eyes, mouth pain, mouth sores	Involved in nerve cell regeneration, helping repair the corneal nerve layer. Supports healthy oral mucosa.	Meat, fish, eggs, dairy, fortified cereals.
Vitamin D	Dry eyes, burning mouth syndrome	Modulates inflammation and immune responses, which can affect tear quality and oral moisture.	Sunlight, fatty fish, fortified dairy, egg yolks.
B-Complex	Mouth sores, inflamed tongue, dry oral mucous membranes	Supports the integrity of mucous membranes throughout the body.	Whole grains, meat, dairy, eggs, fish.

Beyond Nutritional Deficiencies: Other Causes

It is important to recognize that dry eyes and mouth are not always caused by a simple vitamin deficiency. Other significant factors may be at play, and it is crucial to consult a healthcare professional for a proper diagnosis.

Autoimmune diseases

Autoimmune disorders are a major cause of dry eyes and mouth, as the immune system mistakenly attacks the body's moisture-producing glands.

Sjögren's Syndrome: This is a chronic autoimmune disease specifically characterized by dry eyes (due to damage to the lacrimal glands) and dry mouth (due to damage to the salivary glands). It can occur alone or alongside other autoimmune conditions like lupus.

Medications and other factors

Medications: Many common drugs, including antidepressants, antihistamines, diuretics, and blood pressure medication, can cause dry mouth as a side effect by affecting saliva production.
Thyroid problems: Conditions like Hashimoto's disease can disrupt the immune system and eventually lead to chronic dry mouth.
Lifestyle factors: Dehydration, smoking, alcohol consumption, and persistent mouth-breathing can all contribute to dryness.
Chronic illness: Diabetes is another condition frequently associated with dry mouth.

The importance of addressing the root cause

While supplementation can be beneficial, particularly for diagnosed deficiencies, it is often not a complete solution. In cases of autoimmune disease or medication side effects, managing the underlying condition is essential. Your doctor may recommend a range of therapies, from artificial tears and saliva substitutes to specific treatments for the primary disease.

Conclusion

For those wondering what vitamin deficiency causes dry eyes and mouth, the answer most prominently points to vitamin A, which is crucial for the health of your eyes' mucous membranes. However, several other nutrients, including vitamin B12, other B-complex vitamins, and vitamin D, also play a significant role. It is vital to consult a healthcare provider to determine the exact cause of your symptoms, as they can also stem from autoimmune diseases like Sjögren's syndrome, certain medications, or other health issues. A balanced diet is always the best defense against deficiencies, but supplements may be necessary under medical guidance. Early diagnosis and appropriate treatment are key to alleviating discomfort and preventing long-term complications.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Consult a healthcare professional for diagnosis and treatment.

Frequently Asked Questions

A doctor can diagnose a vitamin deficiency through a blood test. If your symptoms improve with supplementation, it may indicate a deficiency, but other conditions must be ruled out by a medical professional.

No, severe vitamin A deficiency is rare in developed countries but still affects vulnerable populations in low-income nations. It is most often linked to inadequate dietary intake.

Sjögren's syndrome is an autoimmune disease where the body attacks its own moisture glands. Unlike a vitamin deficiency, it is not cured by adding vitamins but requires specific management by a rheumatologist.

It is not recommended to self-prescribe supplements. Over-supplementation, especially with fat-soluble vitamins like A and D, can be toxic. Always consult a healthcare provider for the correct diagnosis and dosage.

Not necessarily. While they can occur together due to systemic issues like Sjögren's syndrome or certain nutritional deficiencies (e.g., vitamin A), their causes can be independent. For example, some B vitamin issues might affect the mouth more, while others are more critical for eye health.

Eating a balanced diet rich in whole foods is key. Good choices include leafy greens, eggs, fish, and colorful fruits and vegetables to ensure sufficient intake of vitamins A, B, and D, as well as essential minerals.

Staying hydrated with plenty of water, using a humidifier, and chewing sugar-free gum to stimulate saliva are helpful strategies. For severe symptoms, artificial tears or artificial saliva substitutes may be recommended.