The Chemistry of Citric Acid (C₆H₈O₇) in Skincare and Other Benefits: Amazing Guide

Citrus fruits, including lemons, oranges, and grapefruits, naturally contain citric acid, a mild organic acid. Citric acid has the chemical formula C6H8O7. It possesses three carboxylic acid functional groups, making it a tricarboxylic acid. It has a nice, acidic flavor and appears as a white, crystalline powder or granule that dissolves in water. With a pH of about 2.2 and a melting point of about 153–159°C, citric acid is a weak mineral acid that is acidic but less corrosive than strong mineral acids like hydrochloric acid or sulfuric acid.

Citric acid is a versatile substance that has a wide range of uses in many sectors. It is a valuable element in food, drinks, cleaning goods, pharmaceuticals, and numerous industrial processes due to its natural origin, acidity, and chelating qualities. As a potent and advantageous chemical, citric acid has earned a position in skincare products. Citric acid in skincare routine is a beneficial addition due to its exfoliating, brightening, antioxidant, and sebum-regulating qualities. Utilizing citric acid to its full capacity will help you achieve healthier, more beautiful skin.

Here are some examples of fruits and vegetables that contain citric acid:

  1. Lemons: Lemons are well-known for their high citric acid content and for being very acidic.
  2. Oranges: Citric acid is abundant in oranges, particularly sour kinds like Seville oranges.
  3. Grapefruits: Like lemons and oranges, grapefruits contain a sizable amount of citric acid.
  4.  Lime: Another citrus fruit with a reputation for acidity and citric acid content is lime.
  5. Tomatoes: Fruit with many uses and a source of citric acid. They are frequently used in salads and savory recipes.
  6. Kiwi: Due in part to their high citric acid concentration, kiwi fruits are renowned for their vivid green colour and reviving flavor.
  7. Grapes: Citric acid, which is present in some grape varietals, particularly green grapes, gives grapes their acidic and sweet flavor.
  8. Apples: Apples, especially tart kinds like Granny Smith apples, contain traces of citric and malic acids.
  9. Strawberries: Strawberries have a tart flavor and include other organic acids, such as citric acid.
  10. Blackberries: These berries have a sour flavor and are high in citric acid.
  11. Pineapple: This tropical fruit’s distinctive sweet and tangy flavor is a result of citric acid.

Citric acid in skincare:

Due to its advantageous qualities, it is a versatile element used in many skincare products. It’s crucial to take your skin type and sensitivity into account when using skincare products that include citric acid. It may irritate some people more easily, especially if they have sensitive or reactive skin. It is usually advised to conduct a patch test prior to utilizing new goods and to adhere to the manufacturer’s guidelines. The following common skincare items may include citric acid:

  1. Face Cleansers: It is frequently used as face cleansers to aid in exfoliation and the removal of dead skin cells, which helps to promote a smoother and more radiant complexion.
  2. Toners: Citric acid-containing toners can balance the pH of the skin, tighten pores, and enhance the texture of the skin. They may also increase the efficiency of later-applied skincare products.
  3. Face Masks: Some face masks, especially those that target dull or uneven skin tone, contain it. It aids in exfoliation and skin radiance for a more radiant appearance.
  4. Spot Treatments: It can be used to treat acne-prone skin for spot treatments. It promotes a brighter complexion, lessens excess oil, and helps to unclog pores.
  5. Body Scrubs: Due to their exfoliating qualities, it is a frequent ingredient in body scrubs. Dead skin cells are removed, and the skin’s texture is improved.
  6. Hair Care Products: It is occasionally used to help eliminate buildup and improve shine in hair care products, including shampoos and conditioners.
  7. Anti-Aging Serums: Some anti-aging serums contain citric acid to boost collagen formation, accelerate skin cell turnover, and lessen the appearance of fine lines and wrinkles.

It’s also crucial to keep in mind that citric acid in skincare might make skin more sensitive to sunlight, so when using skincare products with this ingredient, you should wear enough sun protection.

Advantages of citric acid:

Citric acid in skincare products is a commonly used ingredient due to its beneficial properties for the skin. Here are some details about its use in skincare:

  • Exfoliation: Because citric acid is an alpha-hydroxy acid (AHA), it can exfoliate skin as it helps to remove dead cells from the skin surface, boosting cell renewal and exposing younger, smoother skin underneath. This exfoliating process can improve the skin’s tone and texture, lessen the visibility of fine lines and wrinkles, and improve the complexion’s overall shine.
  • pH Balancing: The skin’s normal pH is somewhat acidic, hovering between 4.5 and 5.5. By neutralizing alkaline effects and reestablishing the skin’s ideal acidic environment, citric acid aids in maintaining the pH of the skin in balance. For healthy skin to function, the right pH balance must be maintained because it supports the skin’s protective barrier and aids in avoiding problems like dryness, irritation, and breakouts. 
  • Astringent Properties: Citric acid contains mild astringent characteristics, which means they can help firm and tighten the skin. It can reduce the visibility of pores, making the skin look smoother and more polished.
  • Skin Brightening: Citric acid can lighten skin. Dark spots, hyperpigmentation, and uneven skin tone can all be diminished with its aid. Melanin is the pigment that causes dark spots, and by preventing its synthesis, it can gradually lighten discolored areas.
  • Antioxidant Benefits: Citric acid is an antioxidant, which means it aids in scavenging free radicals that can harm skin cells and speed up the ageing process. Citric acid can protect the skin from external aggressors and preserve a young appearance by lowering oxidative stress.
  • Acne Treatment: Citric acid is helpful for skin that is prone to acne because of its exfoliating and antibacterial characteristics. It facilitates the opening of blocked pores, gets rid of extra oil, and controls the growth of germs that cause acne. Regular application of citric acid can help keep breakouts at bay and enhance the skin’s overall clarity.

With its exfoliating, brightening, pH-balancing, astringent, and antioxidant properties, citric acid is a valuable ingredient in skincare products. Incorporation of citric acid in skincare products can result in a complexion that is healthier and more vibrant.

Disadvantages of citric acid:

Although citric acid in skincare offers several advantages. It’s important to remember that inappropriate or overuse of citric acid might have negative effects on the skin. Citric acid can be a useful ingredient for many people if used properly and in the right formulations. However, before including products containing citric acid in your skincare routine if you have sensitive or reactive skin, you should speak with a dermatologist.

  1. Irritation of the Skin: Citric acid, particularly at high concentrations, can irritate the skin. For those with sensitive or reactive skin, it may induce redness, itching, burning, or stinging feelings. Citric acid-containing products should be patch tested first, and use should be stopped if any negative side effects appear.
  2. Over-Exfoliation: Citric acid, which is an exfoliant, can help in removing dead skin cells. However, over-exfoliation can result from using citric acid-based treatments excessively or frequently. Dryness, irritability, and a weakened skin barrier may result from this. It’s crucial to read product directions carefully and use citric acid-containing products sparingly.
  3. Allergic Reactions: Some people might be allergic to citric acid or experience allergic reactions after using goods that contain it. Rashes, hives, and other skin irritations are examples of allergic reactions. It’s advised to stay away from items containing citric acid if you have a known allergy to acid or citrus fruits.
  4. Interaction with Specific compounds: Citric acid can interact with specific compounds, especially those that have high pH levels. Citric acid can become ineffective or have unfavorable effects when coupled with alkaline substances like baking soda or specific cleaners. It’s crucial to follow the instructions when using citric acid-based goods and to stay away from mixing them with unsuitable components.
  5. Enhanced Sun Sensitivity: Citric acid may increase the skin’s sensitivity to sunlight. It might make the skin more susceptible to UV deterioration, which might result in sunburn or other skin problems caused by the sun. When using products containing citric acid, you must apply sunscreen and take the necessary precautions to protect yourself from the sun.

Synthesis/ Production:

Citric acid is typically produced through a fermentation process using microorganisms, specifically the fungus Aspergillus Niger.

  • The creation of an appropriate substrate is the first step in the fermentation process. Molasses, glucose, or other carbohydrates produced from sources like corn, sugarcane, or beets are examples of common substrates. 
  • The substrate is sterilized to get rid of any unwelcome microbes. After that, an Aspergillus Niger culture is added to the substrate. Citrate synthase, an enzyme necessary for the creation of citric acid, can be produced by the fungus.
  • The substrate that has been inoculated is put in a fermentation vessel and kept there under strict monitoring. To maximize the growth of the fungus, this involves controlling the temperature, pH, and oxygen levels. Normally, the fermentation process lasts 5 to 10 days.
  • Citric acid is a result of the fungus’s consumption of the substrate’s carbohydrates as it develops. The citric acid accumulates in the fermentation broth.
  • The broth containing the citric acid is collected after the fermentation process is finished. To separate the fungus’s solid biomass from the liquid in the broth, filtering or centrifugation may be used.
  • Then, using various methods including precipitation, crystallization, or ion exchange chromatography, the citric acid is separated from the fermentation broth. Usually, water content is removed from the purified citric acid by drying it after concentration. This leads to the final powdered or granular form of citric acid being produced.

Chemical Reactions:

It is a versatile compound that can undergo various chemical reactions. Its reactivity and versatility make it useful in a wide range of applications, including food and beverage, pharmaceuticals, cosmetics, and cleaning products. Here are some of the key reactions of citric acid:

  1. Acid-Base Reactions: Citric acid can function as an acid and combine with bases to generate citrate salts. For instance, sodium citrate and water are produced when citric acid and sodium hydroxide (NaOH) react. Carbon dioxide gas, water, and a matching citrate salt can be produced when citric acid reacts with metal carbonates or bicarbonates.

NaOH + C6H8O7 → C6H5O7Na3 + 3H2O

  1. Esterification: In the presence of a potent acid catalyst, alcohols and citric acid can undergo esterification reactions to create esters. In the food business, this reaction is frequently utilized to create flavorings and scents. For instance, ethyl citrate is created when citric acid and C2H5OH combine with an acid catalyst such as H2SO4.

C6H8O7 + 3C2H5OH → C10H16O8 + 3H2O

  1. Dehydration: Under high temperatures, citric acid can undergo dehydration reactions to form H2O and citric acid in anhydrous form. This process is mostly used to produce the powdered or granular form of citric acid. The reaction is reversible, and anhydrous citric acid can absorb moisture from the atmosphere to form the hydrated form.
  2. Oxidation: Citric acid can undergo oxidation reactions under specific conditions. For example, heating citric acid with concentrated sulfuric acid and potassium dichromate can lead to the formation of carbon dioxide, water, and various oxidation products.
  3. Decomposition: At high temperatures, citric acid can undergo thermal decomposition, resulting in the formation of carbon dioxide, water, and other volatile compounds.

Other Applications of citric acid:

Pharmaceutical and Personal Care Products: Citric acid is used as an excipient in tablets and capsules in the pharmaceutical and personal care industries. It aids in improving the stability and solubility of several medications. Due to its antibacterial and tartar-control qualities, it is frequently utilized in mouthwash and toothpaste. Citric acid is mostly used in skin care products due to its functions as a pH adjuster, antioxidant, and preservation agent.

Effective Chelating Agent: Citric acid can bind to metal ions and create stable complexes. It is frequently used to remove metal ions from water, like calcium and magnesium. Citric acid can chelate metal ions in biological systems and facilitate their transit through cell membranes.

Industry of Food and Beverages: In the industry of food and beverages, citric acid is frequently employed as an acidulant and flavoring agent. It imparts a tart flavor, brings out flavors, and serves as a preservative. Soft drinks, fruit juices, candies, jams, jellies, and other processed food items all use it. Effervescent powders, which release carbon dioxide when dissolved in water and give beverages a fizzy effect, are made using citric acid.

Industry of Food and Beverages: Because of its exceptional chelating and descaling qualities, citric acid is a crucial component in many cleaning products. It is a component of descaling agents, bathroom cleaners, kitchen surface cleaners and detergents for dishwashers. Limescale, rust, and hard water stains are all successfully removed from surfaces and machinery using citric acid.

Cosmetics & Personal Care Products: Due to its exfoliating and skin-renewing characteristics, citric acid is utilized in cosmetics as an alpha hydroxy acid (AHA). It supports smoother, more radiant skin by eliminating dead skin cells. It is used to balance pH, improve product stability, and eliminate mineral buildup from the hair in shampoos, conditioners, and hair dyes. Additionally, bath bombs, foot care products, and nail care items all include citric acid.

Applications in Industry: It is also used at the industrial level for the variety of functions, such as water treatment, metal cleaning, and passivation of metal surfaces. It is employed in the printing and dye operations in the textile industry. Additionally, the creation of detergents, the tanning of leather, and the use of buffering agents in biochemical processes all involve the use of citric acid.


Citric acid is a versatile substance that has a wide range of uses in many sectors. It is a valuable element in food, drinks, cleaning goods, pharmaceuticals, and numerous industrial processes due to its natural origin, acidity, and chelating qualities. As a potent and advantageous chemical, citric acid has earned a position in skincare products. It is a beneficial addition to any skincare routine due to its exfoliating, brightening, antioxidant, and sebum-regulating qualities. Utilising citric acid to its full capacity will help you achieve healthier, more beautiful skin.

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How does citric acid play a role in metabolism?

Through the citric acid cycle, commonly referred to as the Krebs cycle or TCA cycle, citric acid plays a critical role in cellular metabolism. It is a crucial component of aerobic respiration because it aids in the breakdown of proteins, lipids, and carbs into ATP, which is then used as energy. In the body, citric acid functions as an antioxidant, aiding in the scavenging of dangerous free radicals. Free radicals can harm cells and have a role in several illnesses, such as cancer, heart disease, and ageing. Citric acid, an antioxidant, aids in the defense of cells against oxidative stress.

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