Skin Infections

Common skin infections could be of viral, fungal and bacterial origin. All these conditions are curable, provided they are diagnosed rightly at the right time and treated.

Viral | Bacterial | Fungal

Viral Infections:

  • Molluscum contagiosum
  • Viral warts
  • Herpes infections
  • Viral exanthems
Bacterial Infections:

  • Impetigo
  • Folliculitis
  • Furuncle (Boil)
  • Erysepelas
  • Cellulitis
  • Abscess
Fungal Infections:

  • Pityriasis versicolor
  • Tinea
  • Candidiasis
  • Seborrhoic dermatitis

Molluscum Contagiosum:

It is a viral infection caused by Molluscum contagiosum Virus belonging to pox virus family. The disease follows contact with the infected persons or contaminated objects. It is commonly seen in children. It is commonly seen in the head and neck region as pearly white, hemispherical lesions with central depression. It easily spreads from one area to the other.

Treatment is extraction or curettage; cryotherapy can be tried.

Viral Warts: These are benign tumors of the skin caused by Human Papilloma Virus (HPV). They can occur at any age but are unusual in infancy. It is spread by direct or indirect contact. Impairment of the epithelial barrier by trauma, xerosis (dry, cracked skin) or maceration (excessive moisture) are pre-requisites for the infection. Warts are commonly seen around the nails, hands, face, feet and genital area. They can spread to other parts of the body through scratching and trauma. Clinically they are seen as asymptomatic, raised, round lesions with rough or velvety surface. On the face, they are seen as fleshy, finger like projections. Patients with defective immunity and those belonging to families with atopy usually develop large number of warts, sometimes resistant to treatment.
Treatment includes

  • Chemical cautery – by using chemicals such a salicylic acid and lactic acid, gluteraldehyde, trichloroacetic acid etc.
  • Electrosurgery
  • Cryotherapy using liquid nitrogen
  • Immunomodulators like podophylline, alpha interferon, 5 fluorouracil, imiquimod
  • CO2 laser

Herpes Infections: These are one of the commonest viral infections of the mucocutaneous surfaces caused by Herpes Simplex Virus (HSV) Type 1 and HSV Type 2. Herpes viruses cause primary mucocutaneous infection on contact with mucosal surfaces or abraded skin following which they replicate and enter the cutaneous neurones. Here they remain dormant and cause recurrent disease whenever the viral reactivation occurs.

HSV Type 1 usually affects the oral cavity and occasionally the eyes. It presents as primary infection or recurrent infection.

Pic: Recurrent herpes labialis

Primary infection usually occurs at younger age and most of the time, goes unnoticed. It is characterised by fever and grouped, fluid filled lesions inside the mouth, leading to multiple, tiny ulcers.

Recurrent herpes labialis is the commonest presentation. It is characterised by a few grouped fluid filled lesions in and around the mouth. It can occur in any individual who had a primary infection (clinical or subclinical) in the past and may be precipitated by fever, stress, UV radiation, dental treatment, surgeries on the face including chemical peeling

Herpes Simplex Type 2 infection occurs over the genitals and is usually sexually transmitted. It also presents as primary and recurrent infection. Primary infection is seen 5-12 days after sexual contact and is clinically characterised by multiple, tiny, grouped, fluid filled lesions which rupture, leaving behind multiple, tiny ulcers over the genitals and is associated with fever and lymph node enlargement. The person with a primary infection will be shedding the virus for about 11-14 days and should avoid sexual contact during this period. Healing occurs in 18-21 days.

Recurrence with HSV 2 infection is more common than HSV 1 infection. However the recurrent attacks are less severe than the primary infection. Recurrence is precipitated by stress, trauma and immunocompromised state. In a recurrence, the viral shedding lasts for 3-4 days and healing occurs in 9-10 days.

Primary genital infection during the third trimester of pregnancy will lead to herpes infection in the neonates which can be severe. With recurrent genital infection, the risk of transmission to the newborn is lower.

Treatment: It should be started early for better results. In addition to the local measures to prevent the infection, acyclovir should be given in appropriate dose for appropriate duration.

Chicken Pox (Varicella): It is an acute infectious disease caused by the Varicella zoster virus. It spreads by inhalations of the viral particles. The duration between the infection and onset of eruption is usually 14-21 days. Most commonly it occurs during childhood when it is less severe and sometimes subclinical. Those who did not have the infection during childhood may develop it later, which might be severe.

Clinically it is characterised by fever, body ache and rash, consisting typically of clear, fluid filled (dew-drop) lesions starting on the trunk and extending on to the face. The lesions crust in 2-4 days and new lesions appear in crops over a period of one week. Patients with varicella are infectious to others when they are having these clear, fluid filled lesions. The lesions of chicken pox usually get secondarily infected resulting in scarring.

Treatment includes rest, use of drying preparations (calamine) in the presence of fluid filled lesions, antibacterial creams for ruptured lesions and antipyretics. Acyclovir is the drug of choice and should be given as early as possible (within 48 hours).

Herpes Zoster: It is a manifestation of reactivation of the Varicella zoster virus that usually remains dormant in a sensory ganglion following chicken pox. It occurs commonly in the elderly, diabetics, immunocompromised and following stress and trauma.

It presents clinically as severe pain along the affected nerve, followed by rash consisting of grouped, fluid filled lesions along the affected nerves. A person with herpes zoster can cause the spread of chicken pox in the family members who did not suffer from it earlier.

Treatment is the same as for chicken pox.

Prevention of varicella is very important in neonates and immunocompromised individuals. Passive immunization is by administering varicella zoster immunoglobulin (VZIg) to abort or modify the clinical infection and should be administered within 4 days of exposure to the infected case. Active immunization with a live attenuated VZ virus reduces the risk of acquiring infection; however it should be given within 48 hours to high risk individuals.

Bacterial Infections

Bacterial infections of the skin are commonly referred to as pyoderma, which literally means pus in the skin. Pathogenic bacteria most commonly causing infections of the skin are coagulase positive Staphylococcus aureus and Streptococcus pyogenes. Conditions predisposing for bacterial infections are moisture, damage to the skin, pre-existing skin disease etc.

While damage to the skin is a pre-requisite for Streptococcal infections, Staphylococcal infections can occur even on intact skin.

Disinfection of the skin using antiseptics can remove the resident flora (non-disease causing bacteria normally present on the skin) that provide defense against infection and hence can predispose to more frequent infections by Staphylococcus aureus. On the other hand, as resident flora do not hinder the growth of Streptococcus pyogenes, disinfecting the skin does not offer protection against this organism either.

Impetigo: It is a common, contagious, superficial infection of the skin caused by either Streptococcus pyogenes or Staphylococcus aureus or both. It is commonly seen in children and young adults. It is common in lower socio-economic groups due to poor hygiene, poor nutrition and over-crowding. The peak incidence is seen in late summer. Precipitating factors include breach in the skin due to trauma, insect bite or any other skin diseases like eczema, infestations (Scabies)

Pic: Bullous Impetigo

Common sites include face, especially around the nose and mouth, scalp and legs.

Treatment: Compresses to remove the crusts followed by application of antibacterial creams.

For mild and localised infections, topical antibiotics like mupirocin, fucidic acid, neomycin and bacitracin combination may suffice.

In the presence of wide spread and severe infections or with associated lymphadenopathy, oral antibiotics are indicated.

Pic: Non-Bullous Impetigo

Once the infection is controlled, the underlying skin disease should be identified and treated.

Info on Bacteria here:


Carbuncle is a deep seated infection of the skin, produced by the infection of neighbouring hair follicles, caused by Staphylococcus aureus. It is predominantly seen in middle aged and elderly men with predisposing causes like diabetes, malnutrition, immunocompromised state (diseases and drugs) and debility. Clinically it presents as painful, hard, red lump with multiple openings discharging pus. Common sites include back of the neck, shoulders, hips and thighs. It is usually associated with fever and generalised weakness. In elderly and debilitated individuals, if not treated in time, it can lead to toxemia and could even be fatal.

Treatment: Pus should be drained. Antibiotics against Staphylococcus aureus should be started as early as possible, drug of choice being cloxacillin or penicillinase resistant antibiotics. Underlying cause should be sought and treated.

Erysepelas: It is the infection of the dermis and the subcutaneous tissue including lymphatics, caused by Streptococcus pyogenes. Clinically it is seen as sharply demarcated, painful, raised, red lesions with orange peel (peau-de-orange) appearance. It is usually associated with fever and lymphadenopathy. The common sites are face and legs. In the presence of lymphatic obstruction secondary to surgery and radiation, it can occur on the upper limbs also. Most important predisposing cause is lymphatic obstruction (filarial lymphedema, varicose veins with chronic edema of limb). It can also occur following injuries, insect bites etc., that act as portal of entry toStreptococcus pyogenes.
Without effective treatment, complications like subcutaneous abscess, cellulitis and septicemia can occur. Sometimes, systemic reactions like nephritis and scarlet fever can follow.

Treatment: Penicillin is the drug of choice. In the presence of severe infection with systemic reaction, injectable penicillin or first generation cephalosporins are indicated. In very early infections and in patients allergic to penicillin, erythromycin is the alternative. Vancomycin can also be used for penicillin sensitive patients with severe infection. Foot end elevation may help in patients with lymphedema. Recurrent erysepelas can occur in patients with chronic lymphedema. In recurrent cases, long term penicillin (Penicillin LA 12L Units once in 3 weeks) can be given. Supportive stockings may also help.

Fungal Infections

Superficial fungal infections of the skin are the most commonly encountered, curable skin diseases. They are caused by fungi belonging to three groups: dermatophytes, Candidaspecies and Malassezia furfur. The fungi affect the skin, hair and nails.

Dermatophytes cause the skin disease known as Tinea (Ring Worm). Dermatophytes infecting the skin could be anthropophilic (human to human), zoophilic (animal to human) or geophilic (soil to human). Most commonly encountered infections are caused by the anthropophilic species. Predisposing factors for dermatophytoses include excessive sweating, occlusive dressing, topical and systemic steroids, underlying skin diseases like ichthyosis and atopic dermatitis, immunocompromised state and environmental factors like high humidity.

The clinical presentation depends upon factors like site of infection, immunological response of the host and species of the fungus (anthropophilic cause less severe and zoophilic cause more severe inflammatory response). Commonly it is seen as ring like lesions with peripheral activity and central clearance. Common sites are the scalp in case of children (Tinea capitis) and body folds (intertriginous) in adults. Itching is a characteristic feature of tinea.

The diagnosis of tinea is to a large extent based on the clinical features. Difficulty arises when the patient presents with tinea incognito (hidden tinea) which results from misdiagnosis and mistreatment with topical steroids, over-the-counter products and home remedies. Tinea is one skin disease that, when diagnosed right and treated right (proper antifungals for proper duration), is curable. Treatment with topical steroids leads to chronic disease.

Differential Diagnosis: Clinically tinea has to be differentiated from common skin diseases like subacute and chronic eczema, psoriasis etc. The points that favour tinea are:

  • Intense itching
  • Sharply demarcated lesions
  • Peripheral activity and central clearance (absent when treated with topical steroids)
  • Asymmetric presentation

In case of doubt, scrapping for fungal elements should be done (if scales are present). If the patient has already used topical steroids, they should be stopped and lesions should be observed or plain antifungals could be advised.

Tinea Capitis resulting in alopecia Tinea Capitis resulting in alopecia
Kerion Tinea Concentricum

Treatment of Tinea: Treatment of tinea includes local application of medicines and oral medications. When the disease is of short duration and localised, local application of medicines is usually sufficient. Long term disease, extensive disease and recurrent infection should be treated with oral medications.

The antifungals used in the treatment of tinea are of two types:

  • Fungistatic agents (inhibit the multiplication of the fungus): Azoles like clotrimazole, miconazole, ketoconazole, oxyconazole etc.
  • Fungicidal agents (kill the fungus): Allylamines like terbinafine, butenafine, naftifine, griseofulvin.

Drugs of choice for dermatophytes are allylamines and griseofulvin.

Duration of treatment depends upon the site of infection. Skin infection usually requires treatment for 4-6 weeks, hair infection for 6-8 weeks and nail infection for months (3-4 months for finger nails, 6-12 months for toe nails).

Treatment should not be discontinued once the itching subsides; it should be continued for the recommended duration to ensure fungal clearance and prevention of immediate relapse. Preventive measures like keeping the area dry, avoiding wet clothes and avoiding friction should be practiced.

Candidiasis: It is the infection of the skin and mucous membranes by yeast like fungus Candida albicans and other species. Cutaneous candidiasis usually affects the web spaces of the fingers and toes, around the nails, body folds and angles of the mouth and genitals.
Cutaneous candidiasis: The factors that favour cutaneous candidiasis are

  • High moisture levels (sweat and prolonged immersion in water)
  • Mechanical trauma (maceration)
  • Obesity
  • Diabetes
  • Immunocompromised states (HIV/AIDS, other causes)
  • Nutritional deficiencies (vitamin, iron deficiency)
  • Cushing’s syndrome (drug induced or neoplastic)
  • Pregnancy
  • Extremes of age

Cutaneous Candidiasis

Clinically, cutaneous candidiasis is characterised by erythema (redness) and maceration with sodden white scales at the periphery of the erythema. In severe cases, there may be tiny, pus filled lesions in the surrounding skin (satellite lesions). There may be associated symptoms of itching and burning.

It has to be differentiated from other types of fungal infections of the folds like tinea and seborroeic dermatitis, Pseudomonas infections of the web spaces, bacterial intertrigo and psoriasis (flexural). Diagnosis can be confirmed by KOH mount.

Treatment: The precipitating factors should be corrected. Topical and systemic antifungals can be used; the drugs of choice would be antifungals belonging to azoles like clotrimazole, miconazole, oxyconazole topically or fluconazole orallly.

Mucosal Candidiasis: It is the Candidal infection of oro-pharyngeal and genital mucosa. It is commonly seen in neonates, elderly, diabetics, immunocompromised (HIV/AIDS), following intake of steroids or of broad spectrum antibiotics, in those wearing dentures, nutritional deficiency etc.

Pics: Oral Candidiasis

Clinically it presents with curdy white patches on the background of erythema (redness) along with a burning sensation. It can affect any part of the oral mucosa or genital mucosa. The most common variety is called the thrush. Following intake of antibiotics, oral candidiasis presents as red mucous membranes with pain, without any white patches. Candidal infection at the angles of the mouth is seen in the elderly due to sagging of the angles and in denture wearers due to ill fitting dentures. It is characterised by erythema, maceration, fissuring and crust formation.

It should be differentiated from other causes of white patches such as leukoplakia, oral lichen planus, lupus eythematoses, frictional keratosis etc.

Treatment: The precipitating factors should be corrected. Topical and systemic antifungals can be used. Nystatin suspension, clotrimazole mouth paints/vaginal tablets topically or fluconazole and itraconazole orallly are used.

Tinea versicolor: It is a common, chronic, non-inflammatory, superficial infection caused by the fungus variably known as Pityrosporum orbiculare, Pityrosporum ovale or Melassezia furfur. It is very common in places with high humidity (tropical climate), affecting 40% of the population. The fungus causing this infection belongs to the normal flora of the skin and the manifestations of the disease occur when there is an increase in the number of the fungi and/or change in the form of the fungi under favourable conditions in the host. The precipitating factors include:

  1. Genetically determined susceptibility
  2. Increased humidity (excessive sweating)
  3. Increased sebum secretion (oily complexion)
  4. Chronic illness
  5. Immunocompromised state
  6. Cushing’s syndrome or prolonged use of glucocorticoids
  7. Excessive use of oils
  8. Pregnancy

Clinically it is characterised by asymptomatic, hypo and/or hyper pigmented tiny patches with fine scaling which becomes prominent on rubbing. The common sites affected are upper trunk, upper arms, neck, axillae (arm pits), face and thighs.

The diagnosis is made on the basis of the clinical presentation and the sites involved. Sometimes it may have to be differentiated from Pityriasis alba (dry, white patches), early vitiligo, indeterminate leprosy, post inflammatory hypopigmentation etc. In case of doubt KOH examination of the scales should be done.

Treatment: Common antifungal agents used are

  • Selenium sulfide 2.5%
  • Topical azoles like clotrimazole, ketoconazole
  • Oral medications like ketoconazole, itraconazole, fluconazole

Duration of treatment is 3 weeks. Repigmentation may take a few months. Relapses are very common and need re-treatment with same drugs.