Dark circles under the eyes are one of the most common skin complaints, and one of the most misunderstood. They are rarely just about tiredness. Genetics, ageing, allergies, and lifestyle habits all play a role, which is why the same under-eye shadows can affect a well-rested 25-year-old and a sleep-deprived 45-year-old for completely different reasons.
Quick Answer
Dark circles are typically caused by thinning skin and visible blood vessels (often genetic or age-related), fluid retention and puffiness, allergies, sun-related pigmentation, or fatigue and dehydration. Most cases are cosmetic, but sudden one-sided darkening or swelling warrants a medical check.
Common Causes of Dark Circles
Genetics and Thin Skin
The skin under the eyes is the thinnest on the body. In some people, especially those with a genetic predisposition, the blood vessels underneath show through more visibly, creating a permanent blue or purple tint regardless of sleep or lifestyle.
Ageing and Collagen Loss
As skin ages, it loses collagen and fat, becoming thinner and more translucent. This makes the dark blood vessels beneath even more visible and can also create hollowing, which casts its own shadow.
Lack of Sleep and Fatigue
Poor or insufficient sleep causes skin to look paler and duller, making underlying blood vessels more prominent. It can also lead to fluid retention and puffiness, which casts shadows that look like darkness. Ongoing tiredness can affect more than your skin. See our guide on why you might feel tired all the time.
Allergies (“Allergic Shiners”)
Allergic reactions trigger histamine release, which dilates blood vessels under the eyes and causes a purplish discolouration known as allergic shiners, often paired with itching, sneezing, or a stuffy nose. Allergies and irritation can also cause visible eye redness. Read more about what causes red eyes.
Sun Exposure and Hyperpigmentation
UV exposure increases melanin production, and the thin under-eye skin is particularly prone to this pigmentation, resulting in a brownish darkening over time.
Dehydration
When the body lacks fluids, the skin beneath the eyes can look dull and sunken, making the area appear darker and more hollow.
Iron Deficiency and Anaemia
Low iron levels reduce oxygen-rich blood flow, which can cause a bluish tint under the eyes along with paleness elsewhere on the skin.
Nasal Congestion
Chronic congestion, whether from a cold or sinus issue, dilates and darkens the veins that drain from the eye area to the nose.
Smoking and Alcohol
Both dehydrate the skin and break down collagen over time, contributing to thinner, more translucent under-eye skin.
How to Reduce Dark Circles
- Prioritise 7 to 9 hours of consistent, quality sleep
- Stay well hydrated throughout the day
- Apply a cold compress to reduce puffiness and constrict blood vessels
- Use sunscreen daily around the eye area to prevent pigmentation
- Try a vitamin C or caffeine-based eye cream to brighten skin and reduce puffiness
- Treat underlying allergies with antihistamines if they are the trigger
- Elevate your head slightly while sleeping to reduce fluid pooling
When to See a Doctor
Dark circles are usually harmless and cosmetic, but you should get checked if you notice:
- Sudden darkening on only one side
- Swelling, pain, or warmth around the eye
- Signs of anaemia such as fatigue, dizziness, or pale skin
- Dark circles that appear alongside unexplained weight changes or other new symptoms
FAQs
Do dark circles always mean I’m not sleeping enough?
No. While poor sleep is a common trigger, genetics, allergies, ageing, and sun exposure are just as often responsible, and improving sleep alone will not fix circles caused by these factors.
Can dark circles be permanent?
Yes, if they are primarily caused by genetics, thin skin, or long-term sun damage, they can persist regardless of lifestyle changes, though their appearance can still be softened with skincare and cosmetic treatments.
Do home remedies like cold spoons or tea bags actually work?
Cold compresses of any kind can temporarily reduce puffiness and constrict blood vessels, giving a short-term brightening effect, but they will not address pigmentation or genetic causes.
Conclusion
Dark circles under the eyes usually come from a mix of genetics, thin skin, allergies, and lifestyle factors like sleep and hydration, rather than a single cause. Identifying which factor applies to you makes it much easier to choose an effective approach, whether that is better sleep habits, allergy treatment, or targeted skincare.
Last reviewed: August 2026. This article is for general information only and does not replace professional medical advice. If you notice sudden or one-sided darkening, please speak to a doctor.
