Atopic dermatitis (eczema) is an itchy inflammation of your skin. It's a long-lasting (chronic) condition that may be accompanied by asthma or hay fever. Eczema is most often seen in infants and children, but it can continue into adulthood or first appear later in life. 

Eczema may affect any area, but it classically appears on your arms and behind the knees. It tends to flare periodically and then subside. 

Causes:   

 May be genetic, but is often allergy related, especially food allergies. It can also be exacerbated by an allergy to dust mites.

In many patients the triggers are unclear.

As it is common in infants and young children and is often considered the precursor to future asthma and allergic rhinitis.

Symptoms

While the signs of eczema may vary person-to-person, the most common symptoms include:

· Dry skin

· Itching

· Red to brownish-gray patches, specially on the hands, feet, ankles, wrists, neck, eyelids, inside the bend of the elbows and knees and for infants on the face or scalp.

Treatment

• Self-care measures, such as avoiding soaps or other irritants and applying creams or ointments, can help relieve itching. 
•  Over-the-counter moisturizers and prescription corticosteroid creams and ointment can help with inflammation. 
• Creams containing calcineurin inhibitors, known as topical immunomodulators, are used to control the skin reaction by altering the immune system.
•  If there is an associated bacterial infection, antibiotic cream or an oral antibiotic may be prescribed.
•  Oral antihistamines can also help severe itching.
•  Non-medical treatments can also be quite effective at treating eczema.
• Wet dressings involve wrapping the affected area with a topical corticosteroid and wet bandages. 
• Light therapy involves exposing the skin to a certain amount of natural sunlight; other forms call for exposure to artificial ultraviolet A and narrow band ultraviolet B (UVB).

Urticaria, also known as hives are raised, red, itchy welts (wheals, or swellings) of various sizes that seem to appear and disappear on your skin.

In most cases, hives and angioedema are harmless and don't leave any lasting marks, even without treatment. The most common treatment for hives and angioedema is antihistamine medications. Serious angioedema can be life-threatening if swelling causes your throat or tongue to block your airway and leads to loss of consciousness. 

Hives can be either acute or chronic.

 Acute urticaria  lasts  less than a day to up to six weeks

 Chronic urticaria last more than six weeks, sometimes occurring for months to years at a time. Mild hives usually aren't life-threatening. You can usually be treated at home. 

The Causes of hives and urticaria may be difficult to determine, especially with chronic urticaria, where it can be up to 50% of the time.

Common Triggers, especially with acute urticaria are:

• Foods: Many foods can cause problems in sensitive people, but shellfish, fish, nuts, eggs, chocolate and milk are frequent offenders. 
• Food additives, such as salicylates and sulfites, are other potential allergens.
• Medications: Almost any medication may cause hives. Common culprits include penicillin, aspirin, ibuprofen (Advil, Motrin), other NSAIDS and blood pressure medications.
• Other Allergens: Other substances that can cause hives include direct contact with pollen, animal dander, latex and insect stings.
• Physical Factors: Environmental factors can result in the release of histamine with subsequent hives or angioedema in some people. Examples of these factors include heat, cold, sunlight, water, pressure on the skin, emotional stress and exercise.
• Dermatographia: The name of this condition literally means "write on the skin." When pressure is applied to the skin or the skin is scratched, raised lines appear on those areas due to histamine-based angioedema that leads to swelling beneath the skin.

In addition to these triggers, hives sometimes occur in response to your body's production of antibodies. This may occur because of blood transfusions; immune system disorders, such as lupus or cancer; certain thyroid disorders; infections, such as hepatitis; or even a cold.