It is possible that your girlfriend is the relatively rare allergic person who
simplySimply sleep has diminished
allergenAllergen
Positive reaction to allergen skin test reactivity. False negativity, is another matter and the most
commonCommon cold causes of total skin test negativity, including histamine, would be: 1) extracts of poor initial or subsequent loss of potency; (2) drugs, especially antihistamines, that modulate the allergic
reactionAllergic reactions
Allergic reactions to medication
Dermatitis, reaction to tinea
Drug allergies
Febrile/cold agglutinins
Insect bite reaction - close-up
Intradermal allergy test reactions
Positive reaction to allergen
Transfusion reaction; (3) diseases, severe debilitating or immunodeficiency diseases (4) reduced reactivity of the skin in infants and elderly patients; (5) improper technique (no or weak puncture); (6) UV exposure; (7) too short/too long an interval from the injection to the interpreted reaction
The most commonly performed skin tests are called ***** skin tests and, with these, the histamine and allergens are injected very superficially. In some instances, these persons will react to deeper injections (intradermal). History of an observed association between exposures to known allergens and worsening asthma can also provide useful information and guide avoidance of precipitants as can any history of seasonal worsening.
You would do well to discuss this with her allergist, asking if any of the above reasons for true or false negative results might be relevant and, especially, if further testing is warranted. You might also ask about other types of testing, such as RAST testing. It would also be of interest to determine if your friend exhibits any of the other signs of allergic disease such as increased numbers of eosinophils in blood and/or sputum and serum IgE levels.
If her severe asthma is not well controlled, it could be because her therapy is sub-optimum, either because of non-prescription or ineffective self-administration. You should also discuss this with her allergist.
Good luck