Understanding Allergic & Reactive Skins

Allergic and reactive skin article

The skin reactions to irritant substances and topical preparations have a long history, and defining the words sensitive/reactive skin is difficult.

To have a sensitive/reactive skin, one must experience adverse reactions in response to different external factors, including cosmetic use or environmental factors. All of the following visible signs or sensations implicate an irritant or allergic reaction.

Erythema, oedema, dryness, stinging, tightness, hot itchy bumps, rashs, small blisters, and comedones & or pustules.

To understand and diagnose sensitive/reactive skin its important to have a comprehensive knowledge of the skin, its immune systems and the role they play in the skin barrier defence system.

Some of the skin’s surface and cellular protection systems are:

  • Acid mantle
  • Stratum corneum
  • Bi-layers
  • Langerhans cell
  • Histidine (antihistamine system)
  • Anti-free radicals
  • Phagocyctes
  • T lymphocytes
  • Lymphatic system
  • Microcirulation.

Any reduction or impairment of the skin barrier defense system will aggravate or compound a predisposition to an allergic response, and reduced barrier function is associated with dry skin, actopic dermatitis and occupation hand eczema.

In addition, from recent research that has led to a better understanding of the Langerhans cells (LCs) role in the skin barrier defense system”. We now know that the epidermis serves as the site that initiates immune responses rather than just a target tissue for a reaction. To define a ‘sensitive/reactive skin’, take careful note of the medical history that is often associated with adverse events.

allergic and reactive skin condition

Look for:

  • Asthma
  • Rheumatoid arthritis
  • Excema
  • Psorasis
  • Hayfever

In addition previous history of:

  • Irritant contact dermatitis
  • Allergic contact dermatitis
  • Immediate contact reaction (urticaria)
  • Acne-genesis and comedone-genisis

From understanding these medical histories, we are led to five categories of ‘sensitive/reactive skin’ sufferers.

Five categories of ‘sensitive/reactive skin’ sufferers:

Medical history associated with adverse events

  1. 1. Individuals with frank dermatological disease.
  2. 2. Individuals with minimal or atypical dermatological disease.
  3. 3. Individuals with previous skin trauma or history.
  4. 4. Individuals with a intrinsic predisposition towards sensitivity/reactive.
  5. 5. Individuals with a extrinsic predisposition towards sensitively/ reactive.

Types of skin reaction associated with medical condition and adverse events

  1. 1. Actopic/sebbhorreic dermatitis, rosacea & ichthyosis.
  2. 2. Mild atopic dermatitis, self prescription or avoidance.
  3. 3. Transient trauma easily linked to an event.
  4. 4. Age, hormones, hereditary.
  5. 5. Work/play lifestyles, environment, topical toiletries, diet.

In beauty/skin treatment therapy, we will find that all of these five categories are part of our day to day work and analysis of the skin. When diagnosing our clients skin the first three are a clear indication of a basic majority of rosacea grades 3-5/reactive.

It is the last two that create for us the most concern in establishing cause of the ‘sensitive/reactive skin’ and treating it.

Most commonly known sensitisers are fragrance 31%, preservatives 25%, and surfactants 12%. Then there is the newer hidden ingredients that affect our skin, causing a problem called compound allergy. These new ingredients are often a mixture of several that are given a trade name. This trade name often makes it very difficult to isolate the one that is causing the allergy, hence the name compound allergy.

In conventional allergic skin reactions, the ingredients of the product known to be allergenic are patch tested individually to identify the allergen(s). The patient is advised to avoid products containing that allergen to avoid further exacerbations of their dermatitis or skin reaction. In the case of compound allergy, no individual ingredient is found to be an allergen on patch testing therefore it is difficult for the patient to avoid certain substances, and must avoid the entire product.However, we have learnt that allergic reactions can take many forms from allergic contact dermatitis through to high erythema or hot itchy bumps and comedones.

A better understanding of commonly known allergens could make our life a little easier, by being vigilant when looking at cosmetic ingredients of products before prescribing them.

There is much literature about the well-known sensitising problems with preservatives and fragrance, there is very little available in the way of specific substances that cause the problems.

The prime area of concern about adverse reactions to chemicals involves the host immune system.

Fragrance allergies, along with reactions to preservatives and surfactants are the most common immunologic responses to cosmetics and toiletries. Once fragrances have penetrated the SC barrier, they may trigger delayed-type hypersensitivity allergic contact dermatitis (ACD)

Phototoxic and photoallergic contact dermatitis:

Photosensitivity: Is the broad term used to describe abnormal or adverse skin reactions to UVR.

Drug induced photosensitivity refers to adverse skin responses which follow the combined or successive exposure to certain chemicals (a photosensitiser) and to UVR. These can be divided into phototoxic and photoallergic reactions.

Photoallergy: Reduced burn time with pigmentation and can be defined as an acquired altered photo-reactivity dependent on an antigen-antibody or cell-mediated hypersensitivity state. (impaired langerhans cell)

Phototoxic: Allergic contact dermatitis with pigmentation and is the common response which will occur in everbody if enough light energy of the proper wave lengths and, in the case of a photosensitised system, enough of the photosensitiser, is present in the skin. Thus, phototoxicity can be likened to a primary irritant response.

Photosensitivity due to topical photosensitisers (photocontact dermatitis) Photosenstivity due to topical photosenstitisers may be phototoxic, photoallergic or a combination of both. It is not always easy to determine whether a particular photosensitivity reaction is phototoxic or photoallergic in nature; a combination of both types of reactions frequently occurs. The most serious consequence of photocontact-allergy is the development of persistent photosensitivity in a small group of patients, despite strict avoidance of further exposure to the photosensitiser.

Erythema potential of commonly used surfactants:

Irritation PotentialSurfactant


  • Amomonium lauryl sulfate
  • Sodium lauryl sulfate
  • Dodecyl trimethyl ammonium bromide
  • Moderate
  • Sodium laureth sulfate – 3EO
  • Triethanolamine lauryl sulfate
  • Soap


  • Sodium laureth sulfate – 7EO
  • Sodium cocoyl isethionate


  • Sodium laureth sulfate – 12EO
  • Polysorbate – 20

Topical photosensitisers

These are chemicals that cause photo contact dermatitis when exposed to UVR.

Chemicals/drugs/substancesActionReaction Cinnamic aldehyde Fragrance Photoallergic 6-methyl coumsrin Fragrance Photoallergic Musk ambrette Perfumes Photoallergic Oak moss Fragrance Photoallergic Bergamot Essential oil Phototoxic Cedar oil Essential oil Phototoxic Citron oil Essential oil Phototoxic Lavender oil Essential oil Phototoxic Lime oil Essential oil Phototoxic Neroli oil Essential oil Phototoxic Petitgrain oil Essential oil Phototoxic Sandalwood oil Essential oil Phototoxic Dimethoxane Preservative Photoallergic Formaldehyde Preservative Erythema

Comedongenic effects of Cosmetic Raw Materials

Although comedones (open or closed) would not be considered an allergy response, they are still a response that can be caused by cosmetic raw ingredients. This type of response, if combined with an active oily skin, would create the type of acne that makes so many dermatologist’s say “stop using too much make-up or skin-care” or “skin-care is bad for your skin”.

Comedongenic effects of Cosmetic Raw Materials


For the skins natural protection systems to function at optimum levels all cells that contribute to that protection system must have a healthy and permeable membrane.

The cutaneous water permeability barrier (TEWL) is attributed to the lipid barrier function of the straum corneum.

That lipid barrier is formed by the differentiation of the keratinocyte from which comes the lipid enriched contents of the epidermal lamellar bodies.(formation of ceramides)

The formation of ceramide 6 is dependant on linoleic acid

These lipids exist in the intercellular spaces of the strautm corneum, they govern the permeability – barrier function of the stratified squamous epithelium. Any reduction in the barrier function is associated with dry skin, actopic dermatitis, sensitive/reactive skins. Including general susceptibility to sensitising substances.

Known as Essential Fatty acid Deficiency or EFAD.

Treatment for EFAD will require the restoration of the ‘skin barrier defense system’, to do this we must replace or enhance the protective lipids that are naturally found in the skin, these include fatty acids, ceramides, cholesterol, linoleic acid and phospholipids. Bearing in mind that many of these are not synthesized by the body and that we are dependant on them being ingested through our daily diet.

Topical application of these types of ingredients provides the raw materials needed by epidermal cells to make lipids, and essential fatty acids are one of the few lipids that can be metabolised from surface application.

Other examples are: phospholipids, lupine seed extract, lecithin, evening primrose oil, tocopherol, flax seed oil. In addition, taking or applying antioxidants that have the ability to fight off environmental assaults, such as UVR, and pollution help protect the skin.

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