When any one of the following three occurs within minutes or hours of exposure to an allergen there is a high likelihood of anaphylaxis:
Involvement of the skin or mucosal tissue plus either respiratory difficulty or a low blood pressure causing symptoms
Two or more of the following symptoms after a likely contact with an allergen:
a. Involvement of the skin or mucosa
b. Respiratory difficulties
c. Low blood pressure
d. Gastrointestinal symptoms
Low blood pressure after exposure to a known allergenSkin involvement may include: hives, itchiness or a swollen tongue among others. Respiratory difficulties may include: shortness of breath, stridor, or low oxygen levels among others. Low blood pressure is defined as a greater than 30% decrease from a persons usual blood pressure. In adults a systolic blood pressure of less than 90 mmHg is often used.During an attack, blood tests for tryptase or histamine (released from mast cells) might be useful in diagnosing anaphylaxis due to insect stings or medications. However these tests are of limited use if the cause is food or if the person has a normal blood pressure, and they are not specific for the diagnosis. Classification
There are three main classifications of anaphylaxis. Anaphylactic shock is associated with systemic vasodilation that causes low blood pressure which is by definition 30% lower than the persons baseline or below standard values. Biphasic anaphylaxis is the recurrence of symptoms within 1–72 hours after resolution of an initial anaphylactic episode. Estimates of incidence vary, between less than 1% and up to 20% of cases. The recurrence typically occurs within 8 hours.
Many of the other drugs have a low to very low risk to develop DIL. The following table shows the risk of development of DIL of some of these drugs on a high to very low scale. High risk:
Procainamide (antiarrhythmic)
Hydralazine (antihypertensive)
Moderate risk:
Quinidine (antiarrhythmic)
Low to Very Low Risk:
Infliximab anti (TNF-α)
Etanercept anti (TNF-α)
Isoniazid (antibiotic)
Minocycline (antibiotic)
Pyrazinamide  (antibiotic)
D-Penicillamine (anti-inflammatory)
Carbamazepine (anticonvulsant)
Oxcarbazepine (anticonvulsant)
Phenytoin (anticonvulsant)
Propafenone (antiarrhythmic)
Chlorpromazine (antipsychotic)
Minoxidil (antihypertensive vasodilator)

Diagnosis
Antinuclear antibodies are usually positive in drug-induced Lupus. Anti-Neutrophil Cytoplasmic antibodies (ANCA) can also be positive in association with certain drugs. Furthermore, anti-histone antibodies can also be positive in drug-induced lupus.Anti-Histone antibodies are positive in up to 95% of patients with drug induced lupus. The most common medications associated with drug induced lupus are hydralazine, procainamide, isoniazid, methyldopa, chlorpromazine, quinidine, and minocycline. Treatment
It is important to recognize early that these drugs are causing DIL like symptoms and discontinue use of the drug. Symptoms of drug-induced lupus erythematosus generally disappear days to weeks after medication use is discontinued. Non-steroidal anti-inflammatory drugs (NSAIDs) will quicken the healing process. Corticosteroids may be used if more severe symptoms of DIL are present. See also
Anti-histone antibody
Lupus erythematosus
Hydralazine
Discoid lupus erythematosus
List of cutaneous conditions

References
External links
eMedicine