Antihistamines Overview

Antihistamines are a type of medication that treats allergy symptoms. Specifically, they block histamine receptors on cells, which consequently reduces physical responses to allergens. Furthermore, when an allergic reaction occurs, a person may experience symptoms such as nasal congestion, sneezing, and itchy skin. Thus, antihistamines can ease these symptoms.

How Does Antihistamines Work?

In fact, an allergic reaction is experienced by a person when contact is made with a safe substance that is understood  by their body as an invading pathogen.

Moreover, substances that trigger allergic reactions are known as allergens, which can include anything from pet dander and pollen to specific proteins found in foods. When an allergen enters a person’s body or touches their skin, histamines are released by cells in the immune system, thereby binding to specific receptors located on cells throughout the body.

As a result, once these receptors are bound by histamines, several typical allergic reactions are started, including the expansion of blood vessels and the tightening of of smooth muscle tissues.

Furthermore, a type of medication that treats allergy symptoms, motion sickness, and some cold and flu symptoms is referred to as antihistamines. Furthermore, H1 histamine receptors are blocked by antihistamines.

What Symptoms Antihistamines Treat?

People can use antihistamines to treat allergic rhinitis, which causes inflammation in the nose.

Antihistamines can help control a wide range of symptoms, such as:

  • Congestion
  • Hives
  • Itchy or watery eyes
  • Skin rashes
  • Itching
  • Nausea
  • Runny nose
  • Sneezing

Types of Antihistamines

A range of antihistamines is available.

First Generation

Firstly, first-generation oral antihistamines, including diphenhydramine (Benadryl) and chlorpheniramine (Chlor-Trimeton), easily cross the blood-brain barrier and affect H1 receptors in the central nervous system (CNS).

Moreover, H1 receptors in the CNS help regulate the body’s sleep-wake cycle.

Consequently, first-generation antihistamines have sedative properties. By doing so, by binding to receptors in the CNS, cognitive and motor functions can be stopped impaired by first-generation antihistamines, causing drowsiness.

In addition, other severe side effects associated with first-generation antihistamines include:

  • Firstly, active liver damage
  • Secondly, dizziness
  • Moreover, poor sleep quality
  • In addition, dry mouth,
  • Finally, low blood pressure.

Examples of First Generation Antihistamines

For example, examples of these antihistamines include:

  • brompheniramine (Dimetane)
  • carbinoxamine (Clistin)
  • clemastine (Tavist)
  • doxylamine (Unisom)
  • hydroxyzine (Atarax, Vistaril)
  • promethazine (Phenergan)
  • triprolidine (Triafed)

Although several types of first-generation antihistamines are available, le, some healthcare professionals may not recommend them if a newer version is available.

Second and Third Generation

On the other hand, second- and third-generation antihistamines do not have sedative properties. Specifically, an article in the journal National Institute of Diabetes and Digestive and Kidney Diseases indicates that second- and third-generation antihistamines are less likely to cross the blood-brain barrier. Thus, this means they do not have such significant effects on the CNS as first-generation types.

The use of these antihistamines is considered safe for adults and children over  12 years old.

It has been stated by the authors of one  2019 review that second- and third-generation antihistamines are safer and more potent than the first-generation types.

Examples of second- and third-generation antihistamines include:

  • Bilastine (Bilaxten),
  • Desloratadine (Clarinex),
  • Loratadine (Claritin),
  • Fexofenadine (Allegra),
  • And rupatadine (Rupafin).

A variety of antihistamines can be purchased by people at their local pharmacies. They are available in several  different forms, such as tablets, gel capsules, nasal sprays, and eye drops.

Types of over-the-counter (OTC) antihistamines include:

  • Benadryl,
  • Chlor-Trimeton,
  • Claritin, Allegra,
  • Tavist, and Zyrtec.

Prescription antihistamines

Prescription from a licensed healthcare professional is required for some types of antihistamines.

In addition, higher concentrations of active ingredients than OTC types may be contained in antihistamines that require prescriptions.

Furthermore, the risk of adverse side effects may require other antihistamines being prescription only

For instance, antihistamines that require a prescription include:

  • Azelastine (Astelin, Astepro, Optivar)
  • Carbinoxamine (Palgic)
  • Desloratadine (Clarinex)
  • Hydroxyzine (Atarax, Vistaril)
  • Levocetirizine (Xyzal)
  • Promethazine (Phenergan)

Moreover, anyone taking antihistamines or any medication should check the label to see which active ingredients are contained in the medication to avoid the risk of an overdose. In particular, if someone overdoses on sedating antihistamines, they may experience cardiac abnormalities or seizures.

Consequently, if an overdose is suspected, immediate medical attention should be sought or the American Association of Poison Control Centers (AAPCC) should be called for advice. 

Generally, most people can safely take low doses of OTC or prescription antihistamines for short periods.

However, antihistamines can cause mild side effects in some people. Specifically, these may include:

Severe Side Effects

Moreover, the severe side effects may include the following:

Furthermore, severe side effects may include the following:

Although rare, mild liver damage may result from long-term use of non-sedating antihistamines (second- and third-generation). For instance, Terfenadine, an antihistamine linked to liver damage, is no longer available for clinical use.

In contrast, most first- and second-generation antihistamines at low doses are considered safe for pregnant women. Nevertheless, high doses of promethazine, a first-generation sedating antihistamine, may cause adverse side effects during pregnancy.

Therefore, pregnant women should consult with their doctor before taking antihistamines, as their doctor can provide appropriate dosage recommendations based on individual symptoms and health.

Summary

Second- or third-generation antihistamines are recommended by most healthcare providers for treating mild to moderate allergy symptoms, such as congestion, watery eyes, and itchy skin. However, you can still buy first-generation antihistamines, although they may cause drowsiness and sedation.

Moreover, a wide range of antihistamines is available for selection in drug stores and online. Therefore, it may be advisable for parents and caregivers to consult a healthcare professional prior to administering an antihistamine to a child, particularly if the child is 12 years old or younger.

Biospecimens

biospecimens

Bay Biosciences is a global leader in providing researchers with high quality, clinical grade, fully characterized human tissue samples, bio-specimens, and human bio-fluid collections.

Human biospecimens are available including cancer (tumor) tissue, cancer serum, cancer plasma, cancer peripheral blood mononuclear cells (PBMC). and human tissue samples from most other therapeutic areas and diseases.

Bay Biosciences maintains and manages its own biorepository, the human tissue bank (biobank) consisting of thousands of diseased samples (specimens) and from normal healthy donors for controls, available in all formats and types.

In fact, our biobank procures and stores fully consented, de-identified and institutional review boards (IRB) approved human tissue samples, human biofluids such as serum samples, plasma samples from various diseases and matched controls.

Also, all our human tissue collections, human biospecimens and human biofluids are provided with detailed, samples associated patient’s clinical data.

In fact, this critical patient’s clinical data includes information relating to their past and current disease, treatment history, lifestyle choices, biomarkers, and genetic information.

Additionally, researchers find the patient’s data associated with the human biospecimens extremely valuable and use it to help identify new effective treatments (drug discovery & development) in oncology, as well as in other therapeutic areas and diseases.

Bay Biosciences banks wide variety of human tissue samples and human biological samples, including fresh frozen human biospecimens cryogenically preserved at – 80°C.

For example fresh frozen tissue samples, tumor tissue samples, formalin-fixed paraffin-embedded (FFPE), tissue slides, with matching human bio-fluids, whole blood and blood-derived products such as human serum, human plasma and human PBMCs.

Bay Biosciences is a global leader in collecting and providing human tissue samples according to the specified requirements and customized, tailor-made collection protocols.

Please contact us anytime to discuss your special research projects and customized human tissue sample requirements.

Types of Biospecimens

Bay Biosciences provides human tissue samples (human specimens) and human biofluids from diseased and normal healthy donors which includes:

Moreover, we can also procure most human biospecimens and human biofluids, special collections and requests for human samples that are difficult to find. All our human tissue samples and human biofluids are procured through IRB-approved clinical protocols and procedures.

In addition to the standard processing protocols, Bay Biosciences can also provide human biofluids such as  human plasma, human serum, and human PBMCs bio-fluid samples using custom processing protocols; you buy donor-specific collections in higher volumes and specified sample aliquots from us.

Bay Biosciences also provides human biospecimens from normal healthy donors; volunteers, for controls and clinical research, Contact us Now.