OBAGI - C® Rx Clarifying Serum - Normal To Oily

Obagi-C® Rx C-Clarifying Serum for Normal to Oily Skin is a 30ml topical solution containing hydroquinone USP 4% (40mg/g) and L-ascorbic acid 10%. It combines prescription hydroquinone with vitamin C in an AM formulation developed for normal, combination and oily skin.

The product is used, when prescribed, for the gradual lightening of melanin-related hyperpigmentation, including melasma, chloasma, freckles and solar or senile lentigines, commonly described as sun spots or age spots.

Product information

• Product: Obagi-C Rx C-Clarifying Serum
• Formulation: Normal to oily skin
• Prescription active ingredient: Hydroquinone USP 4%
• Hydroquinone strength: 40mg per gram
• Vitamin C: L-ascorbic acid 10%
• Quantity: 30ml / 1 fl oz dropper bottle
• Product designation: AM
• Route of administration: External topical use
• Skin types: Normal, combination and oily skin
• Additional label information: Non-comedogenic and non-acnegenic

Indication

The prescribing information describes Obagi-C Rx C-Clarifying Serum as a topical hydroquinone treatment for the gradual lightening of hyperpigmented skin conditions. These include:

• Melasma or chloasma
• Freckles
• Solar or senile lentigines, often called sun spots or age spots
• Other unwanted areas of melanin-related hyperpigmentation where hydroquinone has been prescribed

Skin discolouration can have different causes, and not every form of pigmentation is suitable for treatment with hydroquinone. The condition and intended treatment area should therefore be assessed before use.

Hydroquinone 4%

Hydroquinone is the prescription active ingredient in Obagi-C Rx C-Clarifying Serum. It acts on the process through which melanocytes produce melanin.

The prescribing information states that topical hydroquinone inhibits the enzymatic oxidation of tyrosine to 3,4-dihydroxyphenylalanine, also known as DOPA, and suppresses other melanocyte metabolic processes. This produces a gradual and reversible reduction in pigmentation within the treated area.

L-ascorbic acid 10%

The formulation also contains 10% L-ascorbic acid, the chemically active form of vitamin C. L-ascorbic acid functions as an antioxidant within the formulation and is used in skincare to help neutralise free radicals and support the appearance of more even, brighter-looking skin.

The product label identifies hydroquinone as the prescription active ingredient. L-ascorbic acid is an additional formulation ingredient and should not be confused with the medicinal active ingredient.

Formulation for normal to oily skin

This version of C-Clarifying Serum is specifically labelled for normal to oily skin and is supplied as a liquid serum in an amber glass dropper bottle. The product packaging identifies it as non-comedogenic and non-acnegenic.

The normal-to-oily and normal-to-dry C-Clarifying Serums contain the same headline concentrations of hydroquinone and vitamin C, but their formulation bases are different. They should not be treated as identical products distinguished only by their names.

Normal-to-oily and normal-to-dry formulations

• Normal to oily: Contains hydroquinone 4% and L-ascorbic acid 10% in a base that includes denatured alcohol, dipropylene glycol and fragrance.
• Normal to dry: Contains hydroquinone 4% and L-ascorbic acid 10% but uses a different formulation base without the same normal-to-oily ingredient profile.

The appropriate version depends on skin type, tolerance and the prescribed skincare programme.

Obagi-C Rx and Obagi-C Fx

Obagi-C Rx C-Clarifying Serum contains prescription hydroquinone 4%. It should not be confused with Obagi-C Fx C-Clarifying Serum, which is a separate hydroquinone-free cosmetic formulation.

The Rx and Fx names identify different products with different active-ingredient profiles and regulatory statuses.

Ingredients

Prescription active ingredient: Hydroquinone USP 4% (40mg/g).

Additional identified ingredient: L-ascorbic acid 10%.

The manufacturer lists the formulation ingredients for the normal-to-oily serum as:

Water, propylene glycol, denatured alcohol, dipropylene glycol, ascorbic acid, propylene carbonate, sodium lauryl sulfate and fragrance.

Manufacturer formulations and labelling can change. Anyone with a known ingredient sensitivity should check the ingredient information supplied with the current bottle before use.

How the serum is applied

The bottle and product label identify C-Clarifying Serum for Normal to Oily Skin as an AM product. Apply it only according to the instructions supplied with the individual prescription.

The manufacturer’s general prescribing information states that a thin application may be used once or twice daily, or as directed by the prescribing clinician. The individually prescribed amount and frequency take precedence over general product information.

• Apply only to the intended treatment area.
• Treatment should be limited to relatively small areas at one time.
• Avoid contact with the eyes, nose, mouth and lips.
• If accidental contact occurs, rinse the area thoroughly with water.
• Use appropriate sunscreen and protective measures during treatment and afterwards.

Sun protection

Exposure to sunlight or ultraviolet light can sustain melanocyte activity and contribute to repigmentation. The prescribing information therefore identifies sunscreen use as an essential aspect of topical hydroquinone treatment.

Sun protection should be used consistently during treatment and afterwards, together with any additional protective measures included in the prescribed skincare programme.

Response and treatment duration

Hydroquinone produces a gradual response rather than an immediate change in pigmentation. The manufacturer’s prescribing information states that treatment should be discontinued if no improvement is seen after three months.

The previous description’s claim that improvement may appear within four to six weeks has not been retained because the product-specific prescribing information does not establish that result for every user.

Skin sensitivity and precautions

The manufacturer advises testing for sensitivity by applying a small amount to an unbroken area of skin and checking it within 24 hours. Minor redness may occur. Stop using the serum and obtain advice if itching, blister formation, an excessive inflammatory response or another sign of hypersensitivity develops.

Transient redness or mild burning can occur, and occasional localised contact dermatitis has been reported. Do not use the product if you have previously experienced an allergic reaction to hydroquinone or another ingredient in the formulation.

The safety of topical hydroquinone during pregnancy and in children aged 12 or under has not been established. Caution is also advised during breastfeeding.

Clinical information

The manufacturer’s prescribing information establishes the serum’s hydroquinone concentration, vitamin C content, labelled indications, pharmacological mechanism, formulation ingredients, application range and precautions.

Published studies concerning hydroquinone or vitamin C may involve different formulations, concentrations, treatment combinations and study populations. Results from an individual study should not therefore be presented as product-specific evidence for this exact Obagi-C Rx formulation unless the serum itself was studied.

Storage

Store at a controlled room temperature of 15°C to 25°C and keep the bottle out of direct sunlight. Keep the bottle properly closed and follow any additional storage instructions shown on the supplied packaging.

Frequently asked questions

What is Obagi-C Rx C-Clarifying Serum?

It is a 30ml prescription topical solution containing hydroquinone 4% and L-ascorbic acid 10%. This version is formulated and labelled for normal to oily skin.

Does Obagi C-Clarifying Serum contain hydroquinone?

Yes. The Rx formulation contains hydroquinone USP 4%, equivalent to 40mg of hydroquinone per gram.

How much vitamin C does the serum contain?

Obagi-C Rx C-Clarifying Serum contains 10% L-ascorbic acid, the chemically active form of vitamin C.

Is hydroquinone or vitamin C the prescription active ingredient?

Hydroquinone 4% is identified as the prescription active ingredient. L-ascorbic acid 10% is an additional formulation ingredient.

What is the serum used for?

The prescribing information describes use for gradually lightening hyperpigmented conditions such as melasma, chloasma, freckles, solar or senile lentigines and other unwanted areas of melanin hyperpigmentation.

Is this the normal-to-oily formulation?

Yes. The bottle is labelled for normal to oily skin and is also described by the manufacturer as suitable for combination skin.

Is it non-comedogenic?

Yes. The product packaging identifies the normal-to-oily formulation as non-comedogenic and non-acnegenic.

What is the difference between the normal-to-oily and normal-to-dry serums?

Both contain hydroquinone 4% and L-ascorbic acid 10%, but they use different formulation bases. The normal-to-oily version contains denatured alcohol, dipropylene glycol and fragrance, which are not listed in the same way for the normal-to-dry version.

Is Obagi-C Rx the same as Obagi-C Fx?

No. Obagi-C Rx C-Clarifying Serum contains prescription hydroquinone 4%. Obagi-C Fx is a separate hydroquinone-free cosmetic formulation.

Is this a morning or evening serum?

The product bottle and prescribing label identify the normal-to-oily C-Clarifying Serum as an AM product. Follow the timing and frequency stated on the individual prescription.

How often is C-Clarifying Serum applied?

The general prescribing information states that a thin application may be used once or twice daily or as directed. The individually prescribed frequency should be followed.

How long does the serum take to work?

The response to hydroquinone is gradual and varies according to the pigmentation condition and individual skin response. The manufacturer states that use should be discontinued if no improvement is seen after three months.

Why is sunscreen important?

Ultraviolet exposure can sustain melanocyte activity and contribute to pigmentation returning. Sunscreen and other protective measures are therefore an important part of hydroquinone treatment.

What should I do if the serum causes irritation?

Mild transient redness or burning can occur. Stop applying it and obtain advice if there is itching, blistering, excessive inflammation, persistent irritation or another suspected allergic reaction.

Further ingredient information

Hydroquinone: UK status, formulations and product information