Lemon juice is frequently recommended as a DYI treatment against acne, acne scars and hyperpigmentation. From glossy magazines, beauty blogs, testimonials and even beauticians, everyone seems to promote the use of lemon juice. Could this simple fruit be the answer we all have been looking for?

Alas, probably not. While lemon juice has properties that make it potentially helpful in acne, there are also significant causes for concern. In this post, we’ll look at 7 things you should be aware of before using lemon juice for acne.

Damages the skin barrier

One of the key components of the skin barrier function is the acid mantle, a very fine acidic layer on the skin surface that both supports and promotes the normal native flora and rejects the aggressive and harmful pathogens. The pH of the acid mantle is between 4.5 and 6.5. Disrupting the pH balance leads to skin irritation and weakens the skin barrier function. Lemon juice has a pH between 2 and 3, which makes it problematic for skin care.

At pH 2 lemon juice can damage the skin barrier and lead to skin irritation

A 2005 study compared the effectiveness and irritation potential of salicylic acid formulations with different pH levels. One had pH of 6.9 while the other had pH of 3.3. Results showed that the formulation with pH 3.3 caused 6 times more skin irritation than the formulation with pH 6.9. The acidic formulation also caused more damage to the skin barrier (as measured by water loss) and caused visible reddening of the skin. Both formulations were equally effective at unclogging skin pores.

While there’s no harm in using such acidic formulations now and then, repeated use of highly acidic substances (man-made or natural) can leave your skin irritated and sensitive.

Vitamin C – but not quite enough

Vitamin C is one of the most effective natural topical treatments for acne. Several studies show it’s as effective as benzoyl peroxide and other established treatments. With lemon juice hailed as one of the richest sources of vitamin C, some people believe this is a natural way to give the skin some vitamin C love.

Lemon juice may not have enough vitamin C to be effective against acne

However, the studies on acne used 5% concentration of vitamin C. Lemon juice has orders of magnitude less, about 0.03%. In all fairness, the formulations used in studies used a different form of vitamin C (sodium ascorbyl phosphate). Ascorbic acid (AA), the type found in lemon juice, is likely to be much more effective and requires lower concentration. But even if AA would be 10 times more effective ( a reasonable estimate), lemon juice would still need to have 10 times more AA to qualify as an effective acne treatment. Not to mention that high acidity makes lemon juice a poor choice for daily use.

Squeeze for some anti-aging

Lemon juice contains citric acid, an alpha hydroxy acid (AHA). AHAs are frequently used in cosmetic and anti-aging products as mild exfoliants. Lemon juice contains 8-10% citric acid, the right concentration recommended for a chemical peel.

Lemon juice is a rich source of skin renewing alpha hydroxy acids (AHAs)

While AHAs are great as mild exfoliants and in anti-aging applications, the fact that they are water-soluble makes them a poor choice for acne. AHAs exfoliate and peel the top layer of the skin. While this is helpful, sebum-clogged skin pores are the real problem in acne. Fat-soluble salicylic acid is far better at penetrating into and dissolving these.

Studies have showed that AHA alone, including citric acid, are ineffective against acne comparing to the lipid soluble beta hydroxy acids (BHA), such as salicylic acid. That is why in cosmetic mixtures citric acid is incorporated into a lipid base together with other active ingredients that enhance its potency.

Antibacterial and antifungal

Due to its high acidity, lemon juice considerable lowers the pH, which makes it much harder for bacteria to survive in the skin. This is an indiscriminative property, meaning that lemon juice will also affect both the aggressive pathogens and the skin’s native flora. In acne-prone skin, where elevated pH and overactive native flora becomes more an enemy than a protector the antibacterial features may be helpful.

Surprisingly many side effects

Many people believe that natural ingredients are safe and have no side effects. Lemon juice is a good example of this. Used improperly it can cause skin irritation and hard-to-get-rid-of hyperpigmentation.

Phytophotodermatitis, called lime disease, causes skin irritation, scarring and hyperpigmentation

Many citrus fruits cause phytophotodermatitis. Lemon juice contains furocoumarins, such as psoralen – a chemical with photo-mutagen properties. I wrote about this in detail here. In a nutshell, psoralens react with UV radiation in a way that causes DNA damage in skin cells.

Phytophotodermatitis, not coincidentally called “Lime disease”, has various degrees of skin manifestations such as inflammation, blistering, burning and itching and very likely to create scarring and hyperpigmentation on the affected area. Once again the golden rule for healthy skin must be reminded: always use sunscreen, and especially after you had facial treatments.

Lemon juice also contains potentially irritating substances, such as limonene and citral. Studies have shown that approximately 3% of the normal population may be sensitive to limonene and 1-1.7% to citral. It may seem low, and it is known that natural incidence is usually lower than the results of studies, but is yet another thing to consider when considering lemon juice as an acne treatment.

Lemon juice for acne scars?

Due to its composition and chemical profile lemon juice might not be that useful in treating acne per se but it may help in reducing post-acne hyperpigmentation. Studies have shown AHA formulations can reduce hyperpigmentation, but effective concentrations are much higher than what’s found in lemon juice.

That being said, even low concentrations help to speed up skin renewal and fading of post-acne marks and dark spots.

Final word: Some pros with several cons

As an acne treatment, lemon juice has some pros and several cons. It has the right characteristics and ingredients but not all in the recommended concentrations. There’s also a very real possibility it causes skin irritation and hyperpigmentation.

To benefit from lemon juice’s anti-bacterial and antioxidant properties, you would need to use it daily. But because of its acidity, using lemon juice daily can irritate and damage your skin. You could try diluting it something to bring pH up to more skin-friendly levels.

Because of the real potential for skin irritation and hyperpigmentation, I would advise caution before using lemon juice to treat acne. You can easily find natural skin care products that have all the goodness of lemon juice with minimal side effects.

If you insist on using lemon juice, don’t use it more than 2 to 3 times a week. And use it only in the evenings to minimize the risk of hyperpigmentation from solar radiation.