Breadcrumb
- Home
- Tests, Treatments & Medications
- Medical Tests
- Allergy Tests
Content Map Terms
Tests, Treatments & Medications Categories
-
Medications
- Immunization, Inactivated influenza
- Anthrax Vaccine
- Diphtheria, Pertussis, and Tetanus Vaccines
- Haemophilus Influenzae Type B (Hib) Vaccine
- Hepatitis A Vaccine
- Hepatitis B Vaccine
- Herpes-Zoster Vaccine for Shingles
- Human Papillomavirus (HPV) Vaccine
- Measles, Mumps, and Rubella Vaccine
- Meningococcal Vaccine
- Pneumococcal Vaccines
- Polio Vaccine
- Rotavirus Vaccine
- Weight-Loss Medicines
- Non-Prescription Products for Weight Loss
- Obesity: Should I Take Weight-Loss Medicine?
-
Medical Tests
- Abdominal Ultrasound
- Abdominal X-Ray
- Adrenocorticotropic Hormone
- Alanine Aminotransferase (ALT)
- Albumin Urine Test
- Aldosterone in Blood
- Aldosterone in Urine
- Alkaline Phosphatase
- Allergy Tests
- Alpha-Fetoprotein (AFP) in Blood
- Ambulatory Electrocardiogram
- Ammonia
- Amniocentesis
- Amylase
- Angiogram
- Angiogram of the Head and Neck
- Angiogram of the Lung
- Antinuclear Antibodies (ANA)
- Antisperm Antibody Test
- Antithyroid Antibody Tests
- Arterial Blood Gases
- Arthrogram (Joint X-Ray)
- Arthroscopy
- Aspartate Aminotransferase (AST)
- Autoimmune Disease Tests
- Autopsy
- Barium Enema
- Bilirubin
- Biophysical Profile (BPP)
- Biopsy of Genital Warts
- Bladder Stress Test in Women
- Blood Alcohol
- Blood Culture
- Blood Glucose
- Blood Type Test
- Blood Urea Nitrogen
- Body Temperature
- Bone Biopsy
- Bone Density
- Bone Marrow Aspiration and Biopsy
- Bone Scan
- Bowel Transit Time
- Brain Natriuretic Peptide (BNP) Test
- Breast Biopsy
- Breast Cancer (BRCA) Gene Test
- Breast Ultrasound
- Bronchoscopy
- C-Peptide
- C-Reactive Protein (CRP)
- Calcium (Ca) in Blood
- Calcium (Ca) in Urine
- Cancer Antigen 125 (CA-125)
- Carbon Dioxide
- Carbon Monoxide (CO)
- Carcinoembryonic Antigen (CEA)
- Cardiac Blood Pool Scan
- Cardiac Catheterization
- Cardiac Enzyme Studies
- Cardiac Perfusion Scan
- Catecholamines in Blood
- Catecholamines in Urine
- CD4+ Count
- Celiac Disease Antibodies
- Cell-Free Fetal DNA Test
- Chemistry Screen
- Chest X-Ray
- Chlamydia Tests
- Chloride (Cl)
- Cholesterol and Triglycerides Tests
- Chorionic Villus Sampling (CVS)
- Clinical Breast Examination
- Clostridium Difficile Toxins
- Cold Agglutinins
- Colonoscopy
- Colposcopy and Cervical Biopsy
- Complete Blood Count (CBC)
- Computed Tomography (CT) Scan of the Body
- Computed Tomography (CT) Scan of the Head and Face
- Computed Tomography (CT) Scan of the Spine
- Computed Tomography Angiogram
- Contraction Stress Test
- Coombs Antibody Test
- Coronary Calcium Scan
- Cortisol in Blood
- Cortisol in Urine
- Cranial Ultrasound
- Creatine Kinase
- Creatinine and Creatinine Clearance
- Cystometry
- Bacterial Vaginosis Tests
- Cystoscopy
- Cystourethrogram
- D-Dimer Test
- D-Xylose Absorption Test
- DHEA-S Test
- Dental X-Rays
- Digital Rectal Examination (DRE)
- Doppler Ultrasound
- Ear Examination
- Echocardiogram
- Electrocardiogram
- Electroencephalogram (EEG)
- Electromyogram (EMG) and Nerve Conduction Studies
- Electronystagmography (ENG)
- Electrophysiology Study
- Electrophysiology Tests for the Eyes
- Endometrial Biopsy
- Endoscopic Retrograde Cholangiopancreatogram (ERCP)
- Endoscopic Sinus Examination for Sinusitis
- Esophagus Tests
- Evoked Potential Test for Multiple Sclerosis
- Exercise Electrocardiogram
- Extremity X-Ray
- Facial X-Ray
- Ferritin
- Fertility Awareness
- Fetal Blood Sampling (FBS) for Rh Sensitization During Pregnancy
- Fetal Ultrasound
- Folic Acid Test
- Galactosemia Test
- Gallbladder Scan
- Gallium Scan
- Gastrin
- Genetic Test
- Glycohemoglobin
- Gonioscopy
- Gonorrhea Test
- Growth Hormone
- HIV Viral Load Measurement
- Hair Analysis
- Hearing Tests
- Heart Catheterization for Congenital Heart Defects
- Helicobacter Pylori Tests
- Hemochromatosis Gene Test
- Hemoglobin Electrophoresis
- Hepatitis A Virus Test
- Hepatitis B Virus Tests
- Hepatitis C Virus Tests
- Herpes Tests
- High-Sensitivity C-Reactive Protein
- Home Blood Glucose Test
- Home Blood Pressure Test
- Home Ear Examination
- Home Lung Function Test
- Home Pregnancy Tests
- Homocysteine
- Hormone Inhibin A
- Human Chorionic Gonadotropin (HCG)
- Human Immunodeficiency Virus (HIV) Test
- Human Papillomavirus (HPV) Test
- Hysterosalpingogram
- Hysteroscopy
- Immunoglobulins
- Intravenous Pyelogram (IVP)
- Iron (Fe)
- Joint Fluid Analysis
- KOH Preparation
- Karyotype Test
- Ketones
- Kidney Biopsy
- Kidney Scan
- Kidney Stone Analysis
- Lactic Acid Dehydrogenase (LDH)
- Lactic Acid
- Laparoscopy
- Laryngoscopy
- Lead
- Lipase
- Liver Biopsy
- Liver Function Tests
- Liver and Spleen Scan
- Lumbar Puncture
- Lung Biopsy
- Lung Cancer Screening: Low-Dose CT Scan
- Lung Function Tests
- Lung VQ Scan
- Lyme Disease Test
- Lymph Node Biopsy
- Magnesium (Mg)
- Magnetic Resonance Angiogram (MRA)
- Magnetic Resonance Imaging (MRI) of the Abdomen
- Magnetic Resonance Imaging (MRI) of the Breast
- Magnetic Resonance Imaging (MRI) of the Head
- Magnetic Resonance Imaging (MRI) of the Knee
- Magnetic Resonance Imaging (MRI) of the Shoulder
- Magnetic Resonance Imaging (MRI) of the Spine
- Magnetic Resonance Imaging (MRI)
- Mammogram
- Mediastinoscopy
- Medicine Levels in Blood
- Mental Health Assessment
- Mononucleosis Tests
- Myelogram
- Myoglobin Test
- Needle Puncture and Aspiration of Sinus Contents
- Neurological Examination for Multiple Sclerosis
- Neuropsychological Tests
- Nuchal Translucency Screening Test
- Ophthalmoscopy
- Oral Glucose Tolerance Test
- Overnight Dexamethasone Suppression Test
- Pap Test
- Paracentesis
- Parathyroid Hormone
- Partial Thromboplastin Time
- Pelvic Examination
- Pelvic Ultrasound
- Pericardial Drainage
- Perimetry Test for Glaucoma
- Phenylketonuria (PKU) Test
- Phosphate in Blood
- Phosphate in Urine
- Positron Emission Tomography (PET)
- Potassium (K) in Blood
- Potassium (K) in Urine
- Prealbumin Blood Test
- Prolactin
- Prostate Biopsy
- Prostate-Specific Antigen (PSA)
- Prothrombin Time and INR
- Pulse Measurement
- Radioactive Iodine Uptake Test
- Rapid Strep Test for Strep Throat
- Renin Assay
- Reticulocyte Count
- Retinal Imaging
- Retrograde Pyelogram for Kidney Stones
- Rheumatoid Factor (RF)
- Rubella Test
- Salivary Gland Scan
- Sedimentation Rate
- Seizure Medicine Levels in Blood
- Self-Examination for Dental Plaque
- Semen Analysis
- Sentinel Lymph Node Biopsy
- Serum Osmolality
- Serum Protein Electrophoresis (SPEP)
- Sickle Cell Test
- Sigmoidoscopy
- Single Photon Emission Computed Tomography (SPECT)
- Skin Biopsy
- Skin and Wound Cultures
- Skull X-Ray
- Sleep Studies
- Slit Lamp Examination
- Sodium (Na) in Blood
- Sodium (Na) in Urine
- Sonohysterogram
- Spinal X-Ray
- Sputum Culture
- Sputum Cytology
- Stool Analysis
- Stool Culture
- Stool Tests for Colorectal Cancer
- Swallowing Study
- Sweat Test
- Syphilis Tests
- Tay-Sachs Test
- Testicular Biopsy
- Testicular Examination and Testicular Self-Examination
- Testicular Scan
- Testicular Ultrasound
- Testosterone
- Tests for Erection Problems
- Thick and Thin Blood Smears for Malaria
- Thoracentesis
- Throat Culture
- Thyroid Biopsy
- Thyroid Hormone Tests
- Thyroid Scan
- Thyroid and Parathyroid Ultrasound
- Thyroid-Stimulating Hormone (TSH)
- Tissue Type Test
- Tonometry
- Total Serum Protein
- Toxicology Tests
- Toxoplasmosis Test
- Tuberculin Skin Test
- Tympanocentesis for Ear Infections
- Tympanometry
- Upper Gastrointestinal (UGI) Series
- Upper Gastrointestinal Endoscopy
- Uric Acid in Blood
- Uric Acid in Urine Test
- Urine Culture
- Urine Test
- Urodynamic Tests for Urinary Incontinence
- Vaginal Examination for Preterm Labour
- Vaginal Self-Examination (VSE)
- Vaginal Wet Mount
- Viral Tests
- Vision Tests
- Vitamin B12 Test
- Vitamin D Test
-
Surgery
- Achilles Tendon Rupture: Should I Have Surgery?
- ACL Injury: Should I Have Knee Surgery?
- Blood Transfusions: Should I Bank Blood Before Surgery?
- Bunions: Should I Have Surgery?
- Carpal Tunnel Syndrome: Should I Have Surgery?
- Cataracts: Should I Have Surgery?
- Dupuytren's Disease: Should I Have Hand Surgery?
- Ear Problems: Should My Child Be Treated for Fluid Buildup in the Middle Ear?
- Endometriosis: Should I Have a Hysterectomy and Oophorectomy?
- Enlarged Prostate: Should I Have Surgery?
- Gallstones: Should I Have Gallbladder Surgery?
- GERD: Which Treatment Should I Use?
- Coronary Artery Disease: Should I Have Bypass Surgery?
- Hysterectomy: Should I Also Have My Ovaries Removed?
- Inguinal Hernia: Should I Have Surgery Now, or Should I Wait?
- Lumbar Herniated Disc: Should I Have Surgery?
- Lumbar Spinal Stenosis: Should I Have Surgery?
- Meniscus Tear: Should I Have Surgery?
- Nearsightedness: Should I Have Laser Surgery?
- Pelvic Organ Prolapse: Should I Have Surgery?
- Peripheral Arterial Disease: Should I Have Surgery?
- Plantar Fasciitis: Should I Have Surgery for Heel Pain?
- Rotator Cuff Problems: Should I Have Surgery?
- Scoliosis: Should My Child Have Surgery?
- Sinusitis: Should I Have Surgery?
- Sleep Apnea: Should I Have Surgery?
- Stress Incontinence in Women: Should I Have Surgery?
- Tennis Elbow: Should I Have Surgery?
- Temporomandibular Disorder: Should I Have Surgery for Jaw Pain?
- Tonsillitis: Should My Child Have a Tonsillectomy?
- Ulcerative Colitis: Should I Have Surgery?
- Umbilical Hernia: Should I Have Surgery?
- Umbilical Hernia: Should My Child Have Surgery?
- Uterine Fibroids: Should I Have Surgery?
- Varicose Veins: Should I Have a Surgical Procedure?
- Wisdom Teeth: Should I Have My Wisdom Teeth Removed?
-
Treatments
- Advance Care Planning: Should I Receive CPR and Life Support?
- Advance Care Planning: Should I Stop Treatment That Prolongs My Life?
- Hearing Loss: Should I Get Hearing Aids?
- Atrial Fibrillation: Should I Have Catheter Ablation?
- Hemorrhoids: Which Treatment Should I Use?
- Kidney Failure: What Type of Dialysis Should I Have?
- Low Back Pain: Should I Try Epidural Steroid Shots?
- Obesity: Should I Use a Diet Plan to Lose Weight?
- Warts: Should I Treat Warts?
- First Aid
Test Overview
Allergy testing involves having a skin or blood test to find out what substance, or allergen, may trigger an allergic response in a person. Skin tests are usually done because they are rapid, reliable, and generally less expensive than blood tests, but either type of test may be used.
Skin tests
A small amount of a suspected allergen is placed on or below the skin to see if a reaction develops. There are three types of skin tests:
- Skin prick test. This test is done by placing a drop of a solution containing a possible allergen on the skin, and a series of scratches or needle pricks allows the solution to enter the skin. If the skin develops a red, raised itchy area (called a wheal), it usually means that the person is allergic to that allergen. This is called a positive reaction.
- Intradermal test. During this test, a small amount of the allergen solution is injected into the skin. An intradermal allergy test may be done when a substance does not cause a reaction in the skin prick test but is still suspected as an allergen for that person. The intradermal test is more sensitive than the skin prick test but is more often positive in people who do not have symptoms to that allergen (false-positive test results).
- Skin patch test. For a skin patch test, the allergen solution is placed on a pad that is taped to the skin for 24 to 72 hours. This test is used to detect a skin allergy called contact dermatitis.
Blood test
Allergy blood tests look for substances in the blood called antibodies. Blood tests are not as sensitive as skin tests but are often used for people who are not able to have skin tests.
The most common type of blood test used is the enzyme-linked immunosorbent assay (ELISA, EIA). It measures the blood level of a type of antibody (called immunoglobulin E, or IgE) that the body may make in response to certain allergens. IgE levels are often higher in people who have allergies or asthma.
Other lab testing methods, such as radioallergosorbent testing (RAST) or an immunoassay capture test (ImmunoCAP, UniCAP, or Pharmacia CAP), may be used to provide more information.
Your allergy test results may show that allergy treatment is a choice for you.
Why It Is Done
Allergy testing is done to find out what substances (allergens) may cause an allergic reaction.
Skin test
The skin test can be done to:
- Identify inhaled (airborne) allergens, such as tree, shrub, and weed pollens, moulds, dust, feathers, and pet dander.
- Identify likely food allergens (such as eggs, milk, peanuts, nuts, fish, soy, wheat, or shellfish).
- Find out whether a person may have a drug allergy or be allergic to insect venom.
Blood test
A blood test may be done instead of a skin test if a person:
- Has hives or another skin condition, such as eczema, that makes it hard to see the results of skin testing.
- Cannot stop taking a medicine, such as an antihistamine or tricyclic antidepressant, that may prevent or reduce a reaction to a substance even when a person is allergic to the substance.
- Has had a severe allergic reaction (anaphylaxis).
- Has had positive skin tests to many foods. Blood tests can help find out which foods the person is most likely allergic to.
How To Prepare
Be sure to tell your doctor about all the medicines you take. You may need to stop taking some medicines such as antihistamines for a few days before you have an allergy skin test.
How It Is Done
Allergy skin tests
Skin tests
The health professional doing the skin prick or intradermal test will:
- Clean the test site (usually on your back or arm) with alcohol.
- Place drops of the allergens on your skin about 2.5 cm (1 in.) to 5 cm (2 in.) apart. This allows many substances to be tested at the same time.
- Prick the skin under each drop with a needle. The needle passes through the drop and allows some of the allergen to penetrate your skin. For the intradermal test, a needle is used to inject the allergen solution deeper into the skin.
- Check the skin after 12 to 15 minutes for red, raised itchy areas called wheals. If a wheal forms, it means you are possibly allergic to that allergen (this is called a positive reaction).
Another skin prick method uses a device with 5 to 10 points (heads), which are dipped into bottles that contain the allergen extract. This device is pressed against the skin of the forearm or back so that all heads are pressed into the skin at the same time.
Skin patch test
A skin patch test also uses small doses of the suspected allergen. For this test:
- Doses of allergens are placed on patches that look like adhesive bandages.
- The patches are then placed on the skin (usually on your back). This usually takes about 40 minutes, depending on how many patches are applied.
- You will wear the patches for 24 to 72 hours. Keep the patch area dry when you bathe. And don't do any activities that could make you sweat a lot while you are wearing the patches. This could loosen the patches and cause them to fall off.
- The patches will be removed by your health professional, and your skin will be checked for signs of an allergic reaction.
How long the test takes
Allergy skin tests usually take less than an hour.
Allergy blood tests
A health professional uses a needle to take a blood sample, usually from the arm.
The blood sample will be placed on specially treated paper. It's then sent to a lab to find out if antibodies to any of the allergens being tested are present. If specific antibodies are found, it may mean you are allergic to a certain allergen.
How It Feels
Allergy skin tests
With the skin prick test and the intradermal skin test, you may feel a slight pricking sensation when the skin beneath each sample is pricked or when the needle penetrates your skin.
Allergy blood tests
You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
Risks
Allergy skin tests
The major risk with the skin prick test or the intradermal skin test is a severe allergic reaction called anaphylaxis. Symptoms of this type of reaction include itching, wheezing, swelling of the face or entire body, trouble breathing, nausea, vomiting, and low blood pressure that can lead to shock. An anaphylactic reaction can be life-threatening and is a medical emergency. Emergency care is always needed for this type of reaction. But severe allergic reaction is rare, especially with the skin prick test.
Allergy blood tests
There is very little chance of having a problem from this test. A small bruise may form at the site.
Results
Allergy skin tests
Normal (negative): |
No raised red areas (called wheals) are created by the allergen. |
---|---|
Abnormal (positive): |
A wheal created by the allergen is at least 3 mm (1/8 inch) larger than the reaction to the negative control. The larger the wheal, the more certain it is that the person is allergic to that specific allergen. |
Allergy blood tests
Normal (negative): |
The levels of immunoglobulin E (IgE), a type of antibody, are the same as in a person who does not have allergies. |
---|---|
Abnormal (positive): |
The levels of immunoglobulin E (IgE) antibodies for a particular allergen or group of allergens are above the normal level. |
Related Information
Credits
Current as of: February 27, 2023
Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Martin J. Gabica MD - Family Medicine
Kathleen Romito MD - Family Medicine
Rohit K Katial MD - Allergy and Immunology
Current as of: February 27, 2023
Author: Healthwise Staff
Medical Review:E. Gregory Thompson MD - Internal Medicine & Adam Husney MD - Family Medicine & Martin J. Gabica MD - Family Medicine & Kathleen Romito MD - Family Medicine & Rohit K Katial MD - Allergy and Immunology
This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use and Privacy Policy. Learn how we develop our content.
Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.
HealthLinkBC Files
HealthLinkBC Files are easy-to-understand fact sheets on a range of public health and safety topics including disease prevention and immunizations.
Find Services and Resources
If you are looking for health services in your community, you can use the HealthLinkBC Directory to find hospitals, clinics, and other resources.