Fragrance irritation or allergies are related to four types of physical reaction:

• Contact dermatitis. A localized rash or irritation of the skin that is caused by contact with a substance. There are two types:
  
  
  • Allergic contact dermatitis results from a reaction of the immune system to an allergen. Fragrances are one of the most common triggers of allergic contact dermatitis.
    
    

    
    

  • Irritant contact dermatitis results from coming into contact with a substance that irritates the skin, such as a chemical in some fragrances. It takes a larger amount over a longer period of time for an irritant to cause dermatitis than an allergen.
    
    
• Eczema. A skin condition that is triggered by a substance. Dry flaky skin appears over red, inflamed areas, causing intense itching and burning. People with eczema are most likely to develop contact dermatitis. Eczema caused by allergies may be called atopic dermatitis.
  
  
• Hives. Red, swollen patches of skin that occur in groups and may burn, sting or itch. These are caused by an allergic reaction that causes blood plasma (the fluid portion of blood) to leak into the skin.
  
  

  
  

• Asthma attacks. A condition in which the airways become blocked or narrowed, causing shortness of breath and difficulty breathing. Fragrance irritation or allergies may trigger an asthma attack.
  
  

All four of these reactions may be caused by any number of different substances. A physician can determine whether a patient is experiencing an irritation to a fragrance, sensitivity or an actual allergy. Effective treatment requires identifying the source and nature of the reaction.

People with sensitivity to fragrances may also experience sensitivity to cosmetics, detergents, cleansers, deodorizers and other substances that release chemicals into the air. Studies have indicated that people with pre-existing nasal allergies like hay fever perceive or react more strongly to irritant chemicals. 

Other conditions related to fragrance irritation or allergies include:

• Multiple chemical sensitivity (MCS). MCS is a controversial condition in which exposure to a variety of indoor air pollutants, including fragrances, is believed to cause "allergic" reactions in a small group of highly sensitive people. Some proponents of this theory suggest that it is a new and uncommon form of allergy. Others suggest that it is a stress-related psychosomatic disorder. Psychosomatic disorders are conditions in which emotional factors aggravate physical symptoms. Similar conditions include sick building syndrome which refers to multiple complaints of acute symptoms of irritation and allergy when in a specific building, but then disappear when the person leaves. Single causes of irritation are seldom identifiable in both MCS and sick building syndrome.
  
  
• Occupational rhinitis. An episodic, work-related occurrence of sneezing, nasal discharge and obstruction due to natural or synthetic causes.
  
  

  
  

• Occupational asthma. A common form of industrial lung disease, this form of asthma is triggered by exposure to dust, vapors, gases, fumes or other irritants at a patient’s workplace.

Specialists have found that many people who experience reactions to fragrances are not actually allergic to the chemicals in these products. Instead, the chemicals are irritants, which are generally less responsive to treatment than allergies. Avoiding the offending chemical appears to be the only effective solution, since allergy medications will not affect symptoms of fragrance irritation.