Caffeine
Caffeine is a natural stimulant derived from sources such as coffee beans, tea leaves, and cacao. In skincare, it is valued for its ability to improve circulation, reduce puffiness, and provide antioxidant protection. When applied topically, caffeine constricts blood vessels, which can help diminish the appearance of dark circles and under-eye bags. This vasoconstrictive effect also reduces redness and inflammation, making it beneficial for sensitive or irritated skin.
Beyond its depuffing properties, caffeine is known to enhance microcirculation, temporarily brightening and tightening the skin. It is commonly found in eye creams, facial serums, and body lotions, particularly in formulations designed to target puffiness, fine lines, and uneven skin tone. Its antioxidant properties help neutralize free radicals, protecting the skin from environmental damage that contributes to premature aging. Additionally, caffeine is sometimes included in scalp treatments, as it may help stimulate hair follicles and promote hair growth.
While the effects of caffeine in skincare are generally temporary, regular use can contribute to a more refreshed and toned appearance. It is often paired with other active ingredients to enhance its benefits, making it a popular choice in a variety of skincare formulations.
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class and is the most commonly consumed psychoactive substance globally. It is mainly used for its eugeroic (wakefulness promoting), ergogenic (physical performance-enhancing), or nootropic (cognitive-enhancing) properties. Caffeine acts by blocking binding of adenosine at a number of adenosine receptor types, inhibiting the centrally depressant effects of adenosine and enhancing the release of acetylcholine. Caffeine has a three-dimensional structure similar to that of adenosine, which allows it to bind and block its receptors. Caffeine also increases cyclic AMP levels through nonselective inhibition of phosphodiesterase, increases calcium release from intracellular stores, and antagonizes GABA receptors, although these mechanisms typically occur at concentrations beyond usual human consumption.
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| Pronunciation | /kæˈfiːn, ˈkæfiːn/ | ||
| Other names | Guaranine Methyltheobromine 1,3,7-Trimethylxanthine 7-methyltheophylline Theine | ||
| AHFS/Drugs.com | Monograph | ||
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| Dependence liability | Physical: Moderate 13% and variable low–high 10–73% Psychological: Low–moderate | ||
| Addiction liability | Relatively low: 9% [failed verification] | ||
| Routes of administration | Common: By mouth Medical: Intravenous Uncommon: Insufflation, rectal, transdermal, topical | ||
| Drug class | Stimulant; Adenosinergic; Eugeroic; Nootropic; Anxiogenic; Analeptic; PDE inhibitor; Diuretic | ||
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| Bioavailability | 99% | ||
| Protein binding | 10–36% | ||
| Metabolism | Primary: CYP1A2 Minor: CYP2E1, CYP3A4, CYP2C8, CYP2C9 | ||
| Metabolites | • Paraxanthine 84% • Theobromine 12% • Theophylline 4% | ||
| Onset of action | 45 minutes–1 hour | ||
| Elimination half-life | Adults: 3–7 hours Infants (full term): 8 hours Infants (premature): 100 hours | ||
| Duration of action | 3–4 hours | ||
| Excretion | Urine (100%) | ||
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| ECHA InfoCard | 100.000.329 | ||
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| Formula | C8H10N4O2 | ||
| Molar mass | 194.194 g·mol−1 | ||
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| Density | 1.23 g/cm3 | ||
| Melting point | 235 to 238 °C (455 to 460 °F) (anhydrous) | ||
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| Caffeine (data page) | |||
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Caffeine is a bitter, white crystalline purine, a methylxanthine alkaloid, and is chemically related to the adenine and guanine bases of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). It is found in the seeds, fruits, nuts, or leaves of a number of plants native to Africa, East Asia and South America and helps to protect them against herbivores and from competition by preventing the germination of nearby seeds, as well as encouraging consumption by select animals such as honey bees. The best-known source of caffeine is the coffee bean, the seed of the Coffea plant. People may drink beverages containing caffeine to relieve or prevent drowsiness and to improve cognitive performance. To make these drinks, caffeine is extracted by steeping the plant product in water, a process called infusion. Caffeine-containing drinks, such as coffee, tea, and cola, are consumed globally in high volumes. In 2020, almost 10 million tonnes of coffee beans were consumed globally. Caffeine is the world's most widely consumed psychoactive drug. Unlike most other psychoactive substances, caffeine remains largely unregulated and legal in nearly all parts of the world. Caffeine is also an outlier as its use is seen as socially acceptable in most cultures with it even being encouraged.
Caffeine has both positive and negative health effects. It can treat and prevent the premature infant breathing disorders bronchopulmonary dysplasia of prematurity and apnea of prematurity. Caffeine citrate is on the WHO Model List of Essential Medicines. It may confer a modest protective effect against some diseases, including Parkinson's disease. Some people experience sleep disruption or anxiety if they consume caffeine, but others show little disturbance. Evidence of a risk during pregnancy is equivocal; some authorities recommend that pregnant women limit caffeine to the equivalent of two cups of coffee per day or less. Caffeine can produce a mild form of drug dependence – associated with withdrawal symptoms such as sleepiness, headache, and irritability – when an individual stops using caffeine after repeated daily intake. Tolerance to the autonomic effects of increased blood pressure and heart rate, and increased urine output, develops with chronic use (i.e., these symptoms become less pronounced or do not occur following consistent use).
Caffeine is classified by the U.S. Food and Drug Administration (FDA) as generally recognized as safe. Toxic doses, over 10 grams per day for an adult, are much higher than the typical dose of under 500 milligrams per day. The European Food Safety Authority reported that up to 400 mg of caffeine per day (around 5.7 mg/kg of body mass per day) does not raise safety concerns for non-pregnant adults, while intakes up to 200 mg per day for pregnant and lactating women do not raise safety concerns for the fetus or the breast-fed infants. A cup of coffee contains 80–175 mg of caffeine, depending on what "bean" (seed) is used, how it is roasted, and how it is prepared (e.g., drip, percolation, or espresso). Thus it requires roughly 50–100 ordinary cups of coffee to reach the toxic dose. However, pure powdered caffeine, which is available as a dietary supplement, can be lethal in tablespoon-sized amounts.
