Question:  Freederm is a UK brand of acne and skin care medication that includes an active ingredient used by mouth to treat what ?

Context paragraphs:
Nicotinamide: Nicotinamide (NAA), also known as niacinamide, is a vitamin found in food, used as a dietary supplement, and used as a medication.  As a supplement, it is used by mouth to prevent and treat pellagra (niacin deficiency).  While nicotinic acid (niacin) may be used for this purpose, nicotinamide has the benefit of not causing skin flushing.  As a cream, it is used to treat acne.

Active ingredient: An active ingredient (AI) is the ingredient in a pharmaceutical drug that is biologically active.  The similar terms active pharmaceutical ingredient (API) and bulk active are also used in medicine, and the term active substance may be used for natural products.  Some medication products may contain more than one active ingredient.  The traditional word for the API is pharmacon or pharmakon (from Greek: φάρμακον , adapted from pharmacos) which originally denoted a magical substance or drug.

Clearasil: Clearasil is an American brand of skin care and acne medication, whose products contain chiefly benzoyl peroxide, sulfur & resorcinol, triclosan, or salicylic acid as active ingredients.  Clearasil has a wide range of products both for rapid and sometimes slow acne treatment and for everyday prevention.  The products are marketed to customers worldwide.

Driclor: Driclor is a strong anti-perspirant manufactured by Stiefel Laboratories (UK) and produced in Sligo, Ireland.  Driclor is similar to other strong anti-perspirants using 20% aluminium chloride hexahydrate as the active ingredient, however, the water content and roll-on dispenser may cause skin irritancy as water / perspiration can break down the active ingredient to produce hydrochloric acid.

Aveeno: Aveeno is a brand of skin care and hair care products in the United States owned by American consumer goods and pharmaceutical company Johnson & Johnson.  Aveeno was founded in 1945, and its first product was their Soothing Bath Treatment.  The active ingredient in all Aveeno products are colloidal oats and/or oat extracts - Avenanthramides, which have been branded as "active naturals".  Aveeno offers products to treat skin conditions such as eczema, psoriasis, urushiol-induced contact dermatitis, pruritus ani, chickenpox, hives, and sunburn.

Cleanser: A cleanser is a facial care product that is used to remove make-up, dead skin cells, oil, dirt, and other types of pollutants from the skin of the face.  This helps to unclog pores and prevent skin conditions such as acne.  A cleanser can be used as part of a skin care regimen together with a toner and moisturizer.

Excipient: An excipient is a substance formulated alongside the active ingredient of a medication, included for the purpose of long-term stabilization, bulking up solid formulations that contain potent active ingredients in small amounts (thus often referred to as "bulking agents", "fillers", or "diluents"), or to confer a therapeutic enhancement on the active ingredient in the final dosage form, such as facilitating drug absorption, reducing viscosity, or enhancing solubility.  Excipients can also be useful in the manufacturing process, to aid in the handling of the active substance concerned such as by facilitating powder flowability or non-stick properties, in addition to aiding "in vitro" stability such as prevention of denaturation or aggregation over the expected shelf life.  The selection of appropriate excipients also depends upon the route of administration and the dosage form, as well as the active ingredient and other factors.

Isotretinoin: Isotretinoin, also known as 13-"cis"-retinoic acid (and colloquially referred to by its former brand name Accutane), is a medication primarily used to treat severe acne.  Rarely, it is also used to prevent certain skin cancers (squamous-cell carcinoma), and in the treatment of other cancers.  It is used to treat harlequin-type ichthyosis, a usually lethal skin disease, and lamellar ichthyosis.  It is a retinoid, meaning it is related to vitamin A, and is found in small quantities naturally in the body.  Its isomer, tretinoin, is also an acne drug.

Stridex: Stridex (originally spelled Stri-Dex) is an American acne treatment and prevention medicine, originally registered trademark of Bayer Corporation.  It comes in the form of fibrous pads saturated with astringents and contained in a plastic tub of fifty-five to ninety pads.  Most products in the Stridex line contain as the active ingredient salicylic acid (0.5–2.5%); Stridex "Power Pads", however, contain instead benzoyl peroxide (2.5%), which is considered by medical professionals to be "the most effective and widely used nonprescription medication for both types of acne".  However, they also warn about possible side effects: dryness of the skin, possible burning, and tingling.  Patients are advised to apply treatment with caution around lips, nose and mouth, or cuts and scrapes, and also avoid excessive sun exposure.  In 2013, FDA started to investigate a possible link between benzoyl peroxide- and/or salicylic acid-based acne prevention medicine with hypersensitivity and anaphylactic reactions without calling off any products or placing warnings.

Freederm: Freederm is a UK brand of acne and skin care medication manufactured by Diomed Developments Limited.  The products include Nicotinamide as an active ingredient, which is claimed by the company to be "clinically proven to help get rid of inflamed red spots".

Supporting paragraphs: Freederm Nicotinamide
Answer: pellagra (niacin deficiency)